Story highlights There are no known specific, credible threats 
 
 The bulletin was issued out of an abundance of caution 
 
 (CNN) Federal authorities warned Friday that ISIS sympathizers "continue aspirational calls for attacks on holiday gatherings, including targeting churches." 
 
 The bulletin was issued by the FBI and Department of Homeland Security and issued to law enforcement agencies and private security companies around the US. 
 
 There are no known specific, credible threats, US law enforcement officials say. The bulletin was issued out of an abundance of caution given the public nature of the posted threats and the holiday season. 
 
 The bulletin was sent Friday to law enforcement after pro-ISIS websites had published a publicly-available list of churches in the United States. 
 
 The bulletin also describes the different signs of suspicious activity law enforcement should be aware of. 
 
 Read More ||||| BOSTON (AP) — A knife-wielding man killed by the terror investigators who had him under surveillance was confronted because he had bought knives and talked of an imminent attack on "boys in blue," the FBI said Wednesday. 
 
 In this courtroom sketch, David Wright, left, is depicted standing with his attorney Jessica Hedges, right, during a hearing Wednesday, June 3, 2015, in federal court in Boston. Wright was ordered held... (Associated Press) 
 
 Abdullah Faaruuq, Imam of the Mosque for the Praising of Allah, left, speaks to reporters during a news conference as Darnell Williams, president of the Urban League of Eastern Massachusetts, behind center,... (Associated Press) 
 
 Community members and police officials at Boston Police Department Headquarters prepare to see video, Wednesday, June 3, 2015, in Boston, of a fatal police shooting on Tuesday, in the city's Roslindale... (Associated Press) 
 
 In this courtroom sketch, David Wright, second from left, is depicted standing with his attorney Jessica Hedges, right, as Magistrate Judge M. Page Kelley presides, left, during a hearing Wednesday, June... (Associated Press) 
 
 Darnell Williams, head of the Urban League of Eastern Massachusetts, left, speaks with reporters during a news conference as Rev. Mark Scott, of the Azusa Christian Community church, right, looks on,... (Associated Press) 
 
 Community members and police officials at Boston Police Department Headquarters prepare to see a video, Wednesday, June 3, 2015, in Boston, of a fatal police shooting on Tuesday, in the city's Roslindale... (Associated Press) 
 
 Usaama Rahim plotted for at least a week to attack police, the FBI said in a complaint against a family member who was arrested Tuesday, the day Rahim was shot to death. On Wednesday, the relative, David Wright, was ordered held on a charge of conspiracy with intent to obstruct a federal investigation. 
 
 The FBI said Rahim, who had previously discussed beheadings, bought three fighting knives and a sharpener on or before May 26 and he told Wright on Tuesday he would begin trying to randomly kill police officers. 
 
 An anti-terror task force of FBI agents and Boston police, faced with an imminent threat, confronted Rahim on a sidewalk and fatally shot him when he refused to drop his knife, authorities said. 
 
 An affidavit written by an FBI agent assigned to Boston's Joint Terrorism Task Force refers to a recorded conversation between Rahim and Wright in which Wright made a comparison to "thinking with your head on your chest." The FBI said that was a reference to Islamic State propaganda videos showing severed heads on the chests of beheading victims. 
 
 The FBI affidavit said Rahim initially told Wright about a plan to behead someone outside Massachusetts. On Sunday, Rahim, Wright and an unidentified man met on a beach in Rhode Island to "discuss their plans," the FBI affidavit said. 
 
 "Wright indicated that he agreed with Rahim's plan and supported it," the affidavit states. 
 
 Authorities searched a home in Warwick, Rhode Island, on Tuesday and Wednesday but wouldn't confirm the search was related to the investigation. They also wouldn't confirm how Rahim, 26, and Wright, 24, are related. 
 
 Early Tuesday morning, Rahim called Wright and told him he had changed his plans and no longer planned to kill someone in another state, the affidavit says. Instead, he said he was going to "go after" the "boys in blue," it says, an apparent reference to police officers. 
 
 During the recorded conversation, Rahim told Wright, "Yeah, I'm going to be on vacation right here in Massachusetts. ... I'm just going to, ah, go after them, those boys in blue. Cause, ah, it's the easiest target and, ah, the most common is the easiest for me," the affidavit says. 
 
 The FBI said the phrase "going on vacation" refers to committing violent jihad. 
 
 Authorities allege that during that conversation, Wright advised Rahim to destroy his smartphone, wipe his laptop computer and prepare his will. 
 
 On Wednesday, authorities moved swiftly to manage perceptions of the shooting, which killed a black man whose family is well known among Muslims and African-Americans in Boston. 
 
 Rahim's mother is a nurse at Boston University. His older brother, Ibrahim Rahim, is a scholar known for preaching after the Boston marathon bombings that violence is anti-Islamic. 
 
 Ibrahim Rahim initially posted a message on Facebook alleging police repeatedly shot his brother in the back while he was on a cellphone calling their father for help. But his version unraveled Wednesday after police showed their video of the confrontation to community leaders. 
 
 Darnell Williams, president of the Urban League of Eastern Massachusetts, said he could "150 percent corroborate" the police account. The images clearly show that Usaama Rahim "was not on a cellphone and was not shot in the back," Williams said. 
 
 Police Commissioner William Evans said officers confronted Rahim because "military and law enforcement lives were at threat." 
 
 The video, which police did not make available publicly, shows that Rahim menaced the officers with a large military-style knife and they initially backed away before shooting him when he refused to drop it, police said. 
 
 Williams said he's not ready to call the shooting justifiable, and a Boston Muslim leader, Imam Abdullah Faaruuq, said it was unclear from the "inconclusive" video whether police had to use deadly force. 
 
 "They might have approached him in a different way," Faaruuq said. 
 
 Ibrahim Rahim could not be reached for comment Wednesday as he traveled to Boston to bury his brother. 
 
 Usaama Rahim was under investigation after spreading Islamic State propaganda online and communicating with other people about it, said U.S. Rep. Michael McCaul, who chairs the House Homeland Security Committee. 
 
 "These cases are a reminder of the dangers posed by individuals radicalized through social media," the Texas Republican said. 
 
 Prosecutor Stephanie Siegmann said Wright posed a serious risk of fleeing or obstructing justice if not held pending a June 19 hearing. Wright's attorney, Jessica Hedges, denied that, saying he has deep roots in the Boston area and an "incredibly loving and supportive family." 
 
 Hedges urged the government to be "as transparent as possible" and "abide by the law" as it investigates this case, saying "we have serious concerns about that already." 
 
 Authorities quickly showed the video to black and Muslim community leaders. The meeting "was all about pulling the community together," Evans said. 
 
 After the Boston Marathon bombings in 2013, Ibrahim Rahim described Jihadis who promote terror as "hell-bent on Islam's destruction from within," and he urged fellow Islamic leaders to drive "a mass recall of the rhetoric of hate and to suppress any and all human desire to harm others based on any contrived justification." 
 
 Yusufi Vali, executive director of the Islamic Society of Boston Cultural Center, where Usaama Rahim briefly worked as a guard, said Ibrahim Rahim "is a great guy and preaches a very moderate form of Islam." Vali said Usaama Rahim did not regularly pray at the center and did not volunteer there or serve in any leadership positions. 
 
 Boston voter registration records describe Rahim as a student. Other records show he applied for a security guard license in Florida in 2011 but didn't follow through. A spokeswoman said Rahim had worked for CVS since March. 
 
 Rahim's shooting is being investigated by the Suffolk district attorney's office and the FBI, routine for shootings involving police. The Council of American-Islamic Relations said it's monitoring them. The Black Community Information Center, an activist group in Boston, called for the U.S. Department of Justice to lead a more independent review. 
 
 ___ 
 
 Associated Press writers Collin Binkley and Phil Marcelo contributed to this report from Boston, and Eric Tucker contributed from Washington. 
 
 ___ 
 
 This story has been corrected to show the FBI alleges only Rahim, not Wright, bought three knives. ||||| The FBI and Boston police shot and killed a knife-wielding Roslindale man known for extremist views and arrested another person at an Everett home yesterday as part of an anti-terrorism task force investigation into threats to behead law enforcement officials, the Herald has learned. 
 
 The two-state probe by the Joint Terrorism Task Force included a raid of an Everett triple-decker and an investigation in a Warwick, R.I., neighborhood, all within hours after police say 26-year-old Usaamah Rahim came at cops and an FBI agent with a military-style knife and was shot twice in a Roslindale CVS parking lot around 7 a.m. 
 
 Rahim, who the task force had under 24-hour surveillance for weeks, was later pronounced dead at Brigham and Women’s Hospital. FBI Special Agent in Charge Vincent B. Lisi would only say task force members wanted to “interview him and talk to him about his intentions.” 
 
 A source with knowledge of the investigation told the Herald the probe was sparked by threats calling to cut the heads off law enforcement officials. 
 
 Police Commissioner William B. Evans said authorities knew Rahim “had some extremism as far as his views,” but stopped short of confirming that it was connected to a stream of chilling online calls from ISIS urging its followers around the world to attack law enforcement and military officials. 
 
 In Everett, authorities descended upon a triple-decker on Linden Street where a man was led away by FBI agents at around 5:30 p.m. 
 
 Boston police last night said they were charging a man arrested in Everett who was connected to the probe with conspiracy to commit murder. But the case may be moved to federal court, a law enforcement source said. 
 
 The Roslindale shooting was captured by surveillance video, which Evans said shows Rahim “coming at the officers” as police retreated, telling him to “Drop the knife!” They then shot him twice, once in the torso and abdomen, he said. 
 
 “We believed he was a threat,” Evans said. “He was someone we were watching for quite a time. The level of alarm brought us to question him.” 
 
 Police plan to show the video to community leaders this morning and could release it to the public afterward. 
 
 “It’s our job as community activists to review and expect that information to see whether or not everything was above board and on point,” said Darnell Williams, president of the Urban League of Eastern Massachusetts and one of those invited to screen the surveillance footage. 
 
 The showdown in the Roslindale parking lot erupted at the beginning of the morning commute. 
 
 A Roslindale mother and her 10-year-old son heard the gunfire and saw the aftermath of the police shooting from a second-story window across the street, the mother said. 
 
 Luz Garces, 47, said she was in her kitchen when she heard a “couple” of gunshots, describing two or three rounds, followed by her young son entering the kitchen telling her, “Mommy, Mommy, there was a shooting at the CVS.” 
 
 Imam Ibrahim Rahim, who identified himself as Usaamah Rahim’s brother, said in a Facebook post his younger brother was waiting at a bus stop “to go to his job” when he was approached by police officers. He wrote that his brother was shot three times in the back, and was on the phone with his father “during the confrontation.” 
 
 He said his brother’s last words were, “I can’t breathe.” 
 
 Those were the same words Eric Garner of Staten Island, N.Y., said last year before he died from a chokehold put on him by police. 
 
 Ibrahim Hooper, a spokesman for the Council on American-Islamic Relations, said officials spoke with Ibrahim Rahim, who confirmed it was his brother who was killed. “We’re monitoring the situation to see how it develops,” Hooper told the Herald. “My first question is, what was the probable cause for the stop?” 
 
 Jake Wark, a spokesman for Suffolk District Attorney Daniel F. Conley, said the DA has asked the state medical examiner’s office to expedite Rahim’s autopsy because his family requested that the body be turned over to them so he can be buried within 24 hours of his death as part of their religious beliefs. 
 
 The triple-decker in Everett is well known in the neighborhood as a drug hot spot nicknamed the “Candy Shop,” according to Jim McCabe, 30. A man in a pickup truck drove by later and yelled, “It looks like the Candy Shop is closed!” 
 
 The anti-terrorist probe also reached down to Warwick, R.I., where state police blocked Aspinet Drive and refused to let anyone down the street where neighbors said a home was being searched. It was unclear what authorities were looking for but a law enforcement official familiar with the probe said it was connected to the task force’s investigation. 
 
 Ralph Thomas, 77, of Warwick has a backyard that partially abuts the home, but he said he had no idea what was going on. 
 
 “We don’t really know anybody in back of us,” he said. “You just don’t go back there.” 
 
 Antonio Planas, O’Ryan Johnson and Laurel J. Sweet contributed to this report.
– The country's law-enforcement agencies are being asked to be extra vigilant this holiday weekend after a list of US churches was published on pro-ISIS websites, CNN reports. In a warning issued Friday, the FBI and Department of Homeland Security say ISIS supporters "continue aspirational calls for attacks on holiday gatherings, including targeting churches." According to the Boston Herald, the FBI is looking into the "credibility" of the threats, and none are specific so far. “We continue to work closely with our federal, state, and local law enforcement partners should there be any potential threat to public safety,” CBS New York quotes the FBI as stating. CNN reports the warning was issued "out of an abundance of caution," and the list of US churches is publicly available. Meanwhile, religious leaders in Boston say their followers should show "courage" in celebrating and worshiping as normal this Christmas. “Come to church like you always planned," Rev. Mark Scott tells the Herald. "Church is the safest place you can be."