This undated photo provided by the Houston Police Department shows Joseph James Pappas. Authorities on Wednesday, Aug. 1, 2018, identified a man who they believe gunned down one of former President George... (Associated Press) 
 
 This undated photo provided by the Houston Police Department shows Joseph James Pappas. Authorities on Wednesday, Aug. 1, 2018, identified a man who they believe gunned down one of former President George H.W. Bush's doctors last month as Pappas, the son of a woman who died while the doctor was operating... (Associated Press) 
 
 This undated photo provided by the Houston Police Department shows Joseph James Pappas. Authorities on Wednesday, Aug. 1, 2018, identified a man who they believe gunned down one of former President George H.W. Bush's doctors last month as Pappas, the son of a woman who died while the doctor was operating... (Associated Press) This undated photo provided by the Houston Police Department shows Joseph James Pappas. Authorities on Wednesday, Aug. 1, 2018, identified a man who they believe gunned down one of former President George... (Associated Press) 
 
 HOUSTON (AP) — A man suspected of killing one of former President George H.W. Bush's doctors may have been seeking revenge for his mother, who died on the doctor's operating table more than 20 years ago, authorities said Wednesday. 
 
 Joseph James Pappas, 62, should be considered armed, dangerous and possibly suicidal, Houston police Chief Art Acevedo said at a news conference Wednesday afternoon. 
 
 "There was a lot of planning that went into this. There was a lot of planning and, sadly, some skill," Acevedo said of the July 20 attack on Dr. Mark Hausknecht. Hausknecht was gunned down while riding his bike to work at Houston Methodist Hospital, which is part of the busy Texas Medical Center. Authorities say the shooter rode past Hausknecht before turning around and firing. 
 
 A tip on Tuesday led police to suspect Pappas, the chief said, though he didn't elaborate as to the nature of the tip. 
 
 Acevedo said Pappas hadn't been seen in 36 to 48 hours. He said the last anyone had heard from Pappas was in a Tuesday morning text message in which Pappas wrote that he was going to kill himself. 
 
 Acevedo said police searched his home at 4 a.m. Wednesday and found evidence that ties Pappas to the killing, but he declined to elaborate as to the nature of the evidence. 
 
 The chief said Pappas is white and very fit, and that he's likely getting around on his 10-speed bicycle, which he rides "extensively and almost exclusively." 
 
 Friends and family have described Hausknecht as a humble and generous man who was adored by his patients, volunteered in his community and cared about the environment. 
 
 Hausknecht was also an avid cyclist and rode his bike to work each morning, as he lived less than 2 miles (3.2 kilometers) from his office. 
 
 In 2000, Hausknecht treated Bush for an irregular heartbeat after the ex-president complained about lightheadedness. 
 
 ___ 
 
 Follow Juan A. Lozano on Twitter: https://twitter.com/juanlozano70 ||||| Man with a grudge over mother’s death sought in slaying of Houston doctor 
 
 Houston Police Department chief Art Acevedo releases a photo of Joseph James Pappas, the suspect in the murder of Dr. Mark Hausknecht, during a press conference at HPD headquarters Wednesday, Aug. 1, 2018, in Houston. less Houston Police Department chief Art Acevedo releases a photo of Joseph James Pappas, the suspect in the murder of Dr. Mark Hausknecht, during a press conference at HPD headquarters Wednesday, Aug. 1, 2018, in ... more Photo: Mark Mulligan, Houston Chronicle Photo: Mark Mulligan, Houston Chronicle Image 1 of / 30 Caption Close Man with a grudge over mother’s death sought in slaying of Houston doctor 1 / 30 Back to Gallery 
 
 After apparently nursing a grudge for 20 years, former constable deputy Joseph James Pappas allegedly got on his 10-speed Schwinn bicycle, rode to the Texas Medical Center and gunned down Houston cardiologist Mark Hausknecht in broad daylight, authorities said. 
 
 Police late Wednesday were searching for the accused killer whose mother died on the operating table under Hausknecht's care two decades ago. The 62-year-old may be suicidal and should be considered armed, according to Houston Police Chief Art Acevedo. 
 
 "I don't know when he decided to do this, but I'm very familiar with how this murder was committed and there was a lot of planning that went into this," Acevedo said during an afternoon news conference to announce charges against Pappas. "There was a lot of planning and sadly some skill." 
 
 Five days after Hausknecht's slaying, a man using the same phone number as Pappas tried to sell a stash of weapons, ammunition and tactical vests online. When police searched his Westbury home early Wednesday, he already had given away many of his belongings, according to sources close to the investigation, but he left behind a gun and several holsters. 
 
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 For nearly two weeks, the case baffled police, who pored through surveillance footage as they struggled to solve the brazen July 20 killing. That morning during rush hour, Hausknecht was biking near the intersection of Main and Holcombe when the another man on a bike passed him from behind. Two blocks later, the man turned around on his 10-speed Schwinn bike and fired at least twice. The doctor — a famed physician who once treated former President George H.W. Bush — went down immediately. The gunman rode off in a northbound direction. 
 
 Afterward, Crime Stoppers offered a $5,000 reward for information, but authorities remained tightlipped about their investigation, save for a slow trickle of surveillance video and still photographs from the moments before and after the killing. 
 
 On Monday, one of those videos broke the case. A tipster alerted police to a possible connection to Pappas, whose mother was one of Hausknecht's patients. 
 
 "It appears that this may have been a 20-year-old grudge that this man held," Acevedo told reporters. 
 
 Police kept investigating and eventually learned that Pappas had texted someone he knew indicating he wanted to kill himself, and that he hadn't been heard from in more than a day. Late Tuesday, officers showed up at his home for a welfare check, but Pappas was not there. 
 
 They returned around 4 a.m. Wednesday with a pair of warrants — one to search the house and another to arrest Pappas for murder. 
 
 They did not find their suspect, but they did locate evidence tying him to the killing. 
 
 "We believe that this man is absolutely the killer," Acevedo said, declining to offer more details. As of late Wednesday, Pappas still had not been found. 
 
 "We need to find this guy," the chief said. "This man is dangerous, this man is capable, this man has some skills." 
 
 Until about five years ago, Pappas worked in Harris County law enforcement for roughly three decades, according to state records. From 1997 to 2013, he served as a reserve officer with Harris County Constable Precinct 2, after a number of years on the force there and at Precinct 7. 
 
 At HoustonChronicle.com: Slain Houston doctor remembered at memorial service 
 
 Pappas also had an active real estate license with a business address on Westheimer, and a phone number matching several online weapon sales listings. A call to that number Wednesday went straight to voicemail. 
 
 The items for sale, posted July 25, include two tactical vests, a Smith & Wesson .38-caliber revolver, a $4,500 semi-automatic FN rifle, two sets of ballistic door panels for a Crown Victoria and a box of ammunition. 
 
 An ad on another site in January lists the seller's name as "Joe," notes a southwest Houston location, and offers a variety of ammunition reloading equipment. 
 
 It was unclear whether the guns for sale included the weapon used in the doctor's fatal shooting. Asked for comment, police said they would investigate. 
 
 "We are looking at all aspects of the suspect's life and activities," Acevedo said in a text late Wednesday. 
 
 "It is highly probable he was targeted," Acevedo said in a text message Thursday morning. 
 
 The suspected shooter's neighbors had little to say about him. One woman said she knew he had grown up there, but that they only made neighborly chit-chat and and that he seemed normal. 
 
 A former acquaintance, Yvonne Shaw, said she had stayed with Pappas at his apartment in Houston for about two weeks more than 15 years ago. He told her he worked as an undercover police officer. He seemed caring, she said, but did not like to talk about his job or his past. 
 
 "I couldn't figure anything out, and I didn't want to ask him too much because I hardly knew him," Shaw said, later adding, "I thought he was a little secretive about that stuff." 
 
 The two lost contact when she left Texas, and she had not heard from him since. 
 
 "To me, he was a very nice person," Shaw said. "He cared about people. He didn't seem like someone who would hurt anybody." 
 
 He never talked about his family or his relationship with his mother, she said. However, she said he frequently rode a 10-speed bicycle. 
 
 "He always had it inside so no one would steal it," Shaw said. 
 
 TRIBUTES: Family, friends fondly recall doctor shot while on bike 
 
 Grudge-motivated violence against health-care providers is rare but not unheard of. A 2012 study in Annals of Emergency Medicine identified 154 hospital-related shootings between 2000 and 2011, of which more than 27 percent involved a "determined shooter" harboring a grudge. The victim much more often was a hospital employee than a doctor. 
 
 "Sometimes the hardest part of our job isn't diagnosing or treating the disease, but communicating the gravity of the patient's circumstances," said Dr. Douglas Curran, president of the Texas Medical Association. "It's a struggle. Loved ones can have a hard time comprehending that we can't fix everybody." 
 
 It was not clear what may have prompted the accused killer to act so many years after his mother's death. 
 
 "Never underestimate how deeply people care about and feel the loss of a loved one," said Dr. Edward Poa, a forensic psychiatrist at The Menninger Clinic. "If they blame someone for that loss, they can really want retribution, an eye-for-an-eye sort of thing. They can see their act as righting a wrong." 
 
 The homicide stunned members of the Texas Medical Center Community, including at Houston Methodist, where Hausknecht was an interventional cardiologist. Such specialists treat cardiovascular disease and congenital and structural heart conditions through catheter-based procedures, such as angioplasty and stenting. 
 
 "The Houston Methodist family is still in shock about the senseless killing of one of our longtime physicians, Dr. Mark Hausknecht," said Marc Boom, president and CEO of Houston Methodist. "We are relieved that the Houston Police Department has identified the suspect and are confident he will be apprehended soon." 
 
 Hausknecht, 65, earned his degree from Baylor College of Medicine in 1980, and started practicing in Houston seven years later. He biked to work every day, and took exceptional care of himself, according to those who knew him. 
 
 In 2000, Hausknecht appeared at a news conference at Methodist with Bush after the 41st president was treated for an irregular heartbeat. 
 
 A spokesman for the former president offered prayers and condolence to the doctor's family, colleagues and supporters. 
 
 "Mark was a fantastic cardiologist and a good man," Bush said in a statement. "I will always be grateful for his exceptional, compassionate care. His family is in our prayers." 
 
 The family held a funeral Saturday at First Presbyterian Church. In addition to his wife, Hausknecht is survived by two sons, his mother and three siblings. 
 
 Julian Gill, Fernando Alfonso, Stephen Tucker Paulsen, Victoria Cheyne and Nancy Sarnoff all contributed to this report. ||||| Joseph Pappas, the former Texas constable wanted in the murder of respected Houston cardiologist Mark Hausknecht, has committed suicide and is dead, police say. 
 
 Police previously announced that they suspected Joseph Pappas was the killer of Hausknecht, who was gunned down while riding his bicycle in broad daylight on his way to work. Pappas was also riding a bicycle when he turned around and fired at least twice at the doctor, killing him, police said. The slaying was mysterious because people said Hausknecht had no known enemies; however, police say they believe Pappas, who owned a realty at one point, carried a 20-year grudge against the prominent doctor after his mother died in surgery under Hausknecht’s care. 
 
 “This is our suspect,” police said in announcing the death of Joseph Pappas. 
 
 “This is our suspect.” Police say Joseph Pappas killed himself less than an hour ago. #KHOU11 pic.twitter.com/FoS4HqOgVG — Matt Dougherty (@MattKHOU) August 3, 2018 
 
 Here’s what you need to know: 
 
 Pappas Was Wearing Body Armor When He Shot Himself, Police Say 
 
 #BREAKING: Police say the suspect in the death of a prominent Houston doctor found dead this morning. Investigators say Joseph Pappas committed suicide pic.twitter.com/Pf9hZbeaCb — WBAP 24/7 NEWS (@WBAP247NEWS) August 3, 2018 
 
 Joseph Pappas, who was being actively sought by Houston police and was believed to be dangerous and possibly armed, committed suicide on August 3, 2018, police announced. 
 
 Pappas had “put together an ‘extensive file’ on Dr. Mark Hausknecht before killing him and had a sheet of paper with other names on it,” CBS News reported. 
 
 Joseph Pappas had put together an "extensive file" on Dr. Mark Hausknecht before killing him and had a sheet of paper with other names on it https://t.co/GVgnneU7e4 pic.twitter.com/glOoqe6ohA — CBS News (@CBSNews) August 3, 2018 
 
 Pappas was found dead after committing suicide in southwest Houston. He was wearing body armor and shot himself in the head, police said. 
 
 Joseph Pappas shot, killed himself during encounter with police https://t.co/FejaKGtUlD pic.twitter.com/mFsnS3Au9k — KYTX CBS19 (@kytxcbs19) August 3, 2018 
 
 Pappas “was found with snub-nose revolver, backpack, bulletproof vest and a baseball cap,” reported KPRC-TV. According to Fox26 reporter Sally McDonald, writing on Twitter, “The witness who saw Joseph Pappas works for the Houston Parks Board. He first saw him around 9:20AM near the JCC and believed he looked like the suspect in dr.’s murder. Minutes later he found a wallet Pappas dropped w/ ID in it.” 
 
 At 9:21AM a call came in of an individual chasing a suspicious person. At 9:25 the caller said he was near the Jewish Community Center and that he believed the suspicious person was Joseph Pappas. — Sally MacDonald (@SallyMacFox26) August 3, 2018 
 
 McDonald also reported that it was possible the suspect had been camping while on the run. 
 
 We believe there's a possibility Joseph Pappas was camping in the days since he was identified as the suspect in Dr. Mark Hausknecht's death. Pappas was found dead from a self inflicted gunshot wound. Found w/ a backpack and bullet proof vest under this shirt. @FOX26Houston — Sally MacDonald (@SallyMacFox26) August 3, 2018 
 
 Police feared Pappas might go out in a hail of gunfire, saying, “You don’t normally put on a bulletproof vest when you are thinking about committing suicide.” 
 
 Hausknecht once treated former President George H.W. Bush. The suspect’s full name is Joseph James Pappas, and police said from the start that they believed he was suicidal. 
 
 “He was a brilliant physician, and he’s touched a lot of lives,” Houston Police Chief Art Acevedo said of the victim. The chief extended his condolences to the Hausknecht family. 
 
 Of Pappas, Acevedo said before he was caught: “He’s considered to be armed and dangerous, and people should not try to deal with him directly…Evidence has been obtained that ties this man to this crime, and we believe that this absolutely is the killer of Dr. Hausknecht…He’s very dangerous, and we need to get him into custody.” According to Acevedo, police believe Pappas may have once been a constable years ago in Harris County, Texas. Later news reports confirmed Pappas had worked for years as a deputy constable in Texas. 
 
 The Mother of Joseph Pappas Died Under Dr. Hausknecht’s Care 20 Years Ago, Police Say & Pappas Worked in Law Enforcement 
 
 Police: Houston Dr. Mark Hausknecht killed by man whose mother died during surgery https://t.co/Hng0ThGm2Q pic.twitter.com/TYmmXXQ9Gj — David Cantu (@duckm4st3r) August 1, 2018 
 
 Houston police think the motive dates back 20 years, when the mother of Joseph Pappas died in the care of Mark Hausknecht. They allege that hardened into a “grudge” that never left and spiraled into murder. 
 
 Acevedo said an arrest warrant was issued in the case against Joseph Pappas. “We said we believed he (Hausknecht) was targeted and indeed he was. One of the tips included the fact that the suspect’s mother was a patient of the doctor and died during surgery over 20 years ago,” the chief said. “So it appears this may have been a 20-year-old grudge that this man held.” 
 
 Julia Pappas died in 1997. According to The New York Daily News, Pappas’s father died in 2010, and he also has a sister. 
 
 Asked by a reporter if there were any other links between Hausknecht and Pappas, Acevedo repeated, “He (Hausknecht) operated on his mother 20 years ago and she died during surgery.” He added at another point in the news conference, “The only tie between the doc and him is that we have confirmed his mom died on the operating table…the doctor who’s the victim in this case operated on our suspect’s mom.” 
 
 The chief did not indicate whether there was a trigger that set the suspect off more recently, but he said that multiple firearms were recovered. 
 
 “I don’t know when he decided to do this, but I’m very familiar with how this murder was committed. And there was a lot of planning that went into this. There was a lot of planning and, sadly, some skill. The shots that he took, took some skill,” said Acevedo. He declined to specify more of the evidence that police have recovered in the case. 
 
 You can watch the police chief’s news conference on the suspect here: 
 
 Chief @ArtAcevedo gives update in Homicide investigation re: Dr. Hausknecht https://t.co/hrqsTGvUO6 — Houston Police (@houstonpolice) August 1, 2018 
 
 “Quite frankly, this case has been important to us because you know that the Texas Medical Center is not just a jewel for the people of Houston, it’s a jewel for the state of Texas, for this whole nation,” the chief said. 
 
 Click 2 Houston reported that Pappas worked in law enforcement. He worked “with Harris County Precinct 2 and Precinct 7. He was first paid for his services, and later was listed as a volunteer reserve. Pappas held an armed law enforcement job for more than 30 years, until 2013,” the television station reported, adding that he was not married and lived in the home where he grew up. 
 
 He also had worked as a realtor, according to his LinkedIn page. Click 2 Houston found listings on a site called ArmsList.com by Pappas Realty. KHOU-TV found those and other online listings for “two bullet-proof vests, and listings last week for a $4,500 semi-automatic rifle, a pistol and a bullet-proof panel for a Crown Victoria.” 
 
 According to Harris County court records, Hausknecht had two medical malpractice claims filed against him in civil court in the past but neither involved Pappas as a party. One case was settled and the other is listed as dismissed. 
 
 Houston’s mayor released a statement after police announced the break in the case. 
 
 Mark Hausknecht was a prominent and respected Houston cardiologist who was known for his compassion with patients. 
 
 “Mark was a leader in the Houston Cardiovascular Associates and specialized in cardiovascular disease,” said Houston Methodist, in a statement, adding that Hausknecht was part of the DeBakey Heart & Vascular Center. The family he left behind includes two adult sons, including one who is a medical student. Both sons were Eagle Scouts, a person who knew the family told Heavy. He was married to a doctor named Georgia Hsieh. 
 
 Former patients joined others in offering tributes to the doctor. 
 
 A patient wrote on Facebook, “My heart is broken. The cardiologist Mark Hausknecht was the doctor killed today in Houston. This was my heart Dr. for many years. What a great man and doctor. I had appt next month with him and he just ok my medicine on Monday.” 
 
 There was a $5,000 reward for information leading to an arrest. 
 
 Chief Acevedo said in the news conference that surveillance video and photos authorities previously released in the case gave them their big break after a tipster recognized the person and told police the suspect was allegedly Pappas. 
 
 On July 31, 2018, a tip came to the police chief’s office from “an individual who wanted to provide information on this case,” said Acevedo. 
 
 The police chief praised the community for being a “partner” to helping police “keep neighborhoods safe.” 
 
 Acevedo said the police were able to enhance surveillance video from a home and “individuals recognized this suspect” after that video and photos from it were released to the news media. 
 
 The shooting occurred on July 20, 2018, a Friday, near the Texas Medical Center at around 8:50 a.m. After shooting Dr. Hausknecht, the shooter fled the scene on a bicycle. The murder occurred in the 6700 block of Main Street. 
 
 UPDATE #6: Additional surveillance video released of the suspect in an area neighborhood immediately following the doctor's shooting. No other details at this time. Anyone w/ information urged to contact HPD Homicide at 713-308-3600 or @CrimeStopHOU at 713-222-TIPS. #hounews pic.twitter.com/nWp9EyRQlk — Houston Police (@houstonpolice) July 30, 2018 
 
 In a news conference, authorities said the killer – whom they now suspect was Joseph Pappas – turned to shoot at Hausknecht, firing multiple times. 
 
 “The suspect was on a bicycle as well, rode past the doctor, turned and fired two shots. The doctor went down immediately,” Executive Assistant Chief Troy Finner with the Houston Police Department said during the news conference.
– A man suspected of killing one of former President George HW Bush's doctors may have been seeking revenge for his mother, who died on the doctor's operating table more than 20 years ago, authorities said Wednesday. Joseph James Pappas, 62, should be considered armed, dangerous, and possibly suicidal, Houston police Chief Art Acevedo said at a news conference Wednesday afternoon. "There was a lot of planning that went into this," Acevedo said of the July 20 attack on Dr. Mark Hausknecht, adding that it appears a "20-year-old grudge" led to the attack, per CNN. Hausknecht was gunned down while riding his bike to work at Houston Methodist Hospital, which is part of the busy Texas Medical Center. Authorities say the shooter rode past Hausknecht before turning around and firing. A tip on Tuesday led police to suspect Pappas, the chief said, though he didn't elaborate as to the nature of the tip. Acevedo said Pappas hadn't been seen in 36 to 48 hours, the AP reports. He said the last anyone had heard from Pappas was in a Tuesday morning text message in which Pappas wrote that he was going to kill himself. Acevedo said police searched his home at 4am Wednesday and found evidence that ties Pappas to the killing, but he declined to elaborate as to the nature of the evidence. The chief said Pappas, who was a peace officer in Harris County for three decades per the Houston Chronicle, is white and very fit, and that he's likely getting around on his 10-speed bicycle, which he rides "extensively and almost exclusively." Friends and family have described Hausknecht as a humble and generous man who was adored by his patients, volunteered in his community and cared about the environment. He was also an avid cyclist and rode his bike to work each morning, as he lived less than 2 miles from his office.