People gather for a vigil in the aftermath of a deadly shooting at the Tree of Life Synagogue, in the Squirrel Hill neighborhood of Pittsburgh, Saturday, Oct. 27, 2018. (AP Photo/Matt Rourke) (Associated Press) 
 
 PITTSBURGH (AP) — A gunman who's believed to have spewed anti-Semitic slurs and rhetoric on social media barged into a Pittsburgh synagogue on Saturday and opened fire, killing 11 people in one of the deadliest attacks on Jews in U.S. history. 
 
 The 20-minute attack at Tree of Life Congregation in the Squirrel Hill neighborhood left six others wounded, including four police officers who dashed to the scene, authorities said. 
 
 The suspect, Robert Bowers, traded gunfire with police and was shot several times. Bowers, who was in fair condition at a hospital, was charged late Saturday with 29 federal counts, including hate crimes and weapons offenses. It wasn't immediately known if Bowers had an attorney to speak on his behalf. 
 
 "Please know that justice in this case will be swift and it will be severe," Scott Brady, the chief federal prosecutor in western Pennsylvania, said at a news conference, characterizing the slaughter as a "terrible and unspeakable act of hate." 
 
 The mass shooting came amid a rash of high-profile attacks in an increasingly divided country, one day after a Florida man was arrested and charged with mailing a series of pipe bombs to prominent Democrats and little more than a week before the midterm elections. 
 
 The killings also immediately reignited the longstanding national debate about guns: President Donald Trump said the outcome might have been different if the synagogue "had some kind of protection" from an armed guard, while Pennsylvania's Democratic Gov. Tom Wolf noted that once again "dangerous weapons are putting our citizens in harm's way." 
 
 Trump ordered flags at federal buildings throughout the U.S. to be flown at half-staff in "solemn respect" for the shooting victims. He said he planned to travel to Pittsburgh, but offered no details. 
 
 Authorities say that just before 10 a.m., Bower entered the large synagogue with an assault-style rifle and three handguns. Three separate congregations were conducting Sabbath services in different areas of the large building, according to Michael Eisenberg, the immediate past president of the Tree of Life. The Pennsylvania attorney general's office said it was told by victims that a brit milah — a ritual circumcision ceremony at which a baby boy also receives his Hebrew name — was also taking place, though law enforcement officials later said no children were among the dead or wounded. 
 
 "It is a very horrific crime scene," said a visibly moved Wendell Hissrich, the Pittsburgh public safety director. "It's one of the worst that I've seen." 
 
 The survivors included Daniel Leger, 70, a nurse and hospital chaplain who was in critical condition after undergoing surgery, his brother, Paul Leger, told the Pittsburgh Post-Gazette. Daniel Leger was scheduled to lead a service Saturday morning, he said. 
 
 The mass shooting raised immediate alarm in Jewish communities around the country. Authorities in New York City, Chicago and elsewhere increased security at Jewish centers. 
 
 Bob Jones, head of the FBI's Pittsburgh office, said that worshippers "were brutally murdered by a gunman targeting them simply because of their faith," though he cautioned the shooter's full motive was not yet known. 
 
 Bowers, who had no apparent criminal record, expressed virulently anti-Semitic views on a social media site called Gab, according to an Associated Press review of an archived version of the posts made under his name. The cover photo for his account featured a neo-Nazi symbol, and his recent posts included a photo of a fiery oven like those used in Nazi concentration camps used to cremate Jews during World War II. 
 
 Other posts referenced false conspiracy theories suggesting the Holocaust — in which an estimated 6 million Jews perished — was a hoax. He wrote of a Jewish "infestation," using a slur for Jews. 
 
 Gab confirmed Bowers had a profile on its website, which is popular with far-right extremists. 
 
 Before the shooting, the poster believed to be Bowers also wrote that "HIAS likes to bring invaders in that kill our people. I can't sit by and watch my people get slaughtered. Screw your optics, I'm going in." 
 
 HIAS is a nonprofit group that helps refugees around the world find safety and freedom. The organization says it is guided by Jewish values and history. 
 
 Jonathan Greenblatt, chief executive officer of the Anti-Defamation League, said the group believes Saturday's attack was the deadliest on the Jewish community in U.S. history. 
 
 "Our hearts break for the families of those killed and injured at the Tree of Life Synagogue, and for the entire Jewish community of Pittsburgh," Greenblatt said. 
 
 Israeli Prime Minister Benjamin Netanyahu said he was "heartbroken and appalled" by the attack. 
 
 "The entire people of Israel grieve with the families of the dead," Netanyahu said. "We stand together with the Jewish community of Pittsburgh. We stand together with the American people in the face of this horrendous anti-Semitic brutality. And we all pray for the speedy recovery of the wounded." 
 
 Thousands of people, some holding candles, gathered for a vigil in the Squirrel Hill neighborhood on Saturday night in honor of the victims, whose names were not immediately released. A chant of "vote, vote, vote" broke out during the emotional gathering. Some attendees blamed the shooting on the nation's political climate, and said they took little solace in the planned visit by Trump. 
 
 At a political rally in Murphysboro, Illinois, Trump said "the evil anti-Semitic attack is an assault on all of us." 
 
 The president — who, at times, has been accused by critics of failing to adequately condemn hate, such as when he blamed "both sides" for the violence at a Charlottesville, Virginia, white supremacist rally in 2017 — said that anti-Semitism must be "confronted and condemned everywhere it rears it very ugly head." He called for the imposition of the death penalty for "crimes like this." 
 
 The synagogue is located in the tree-lined residential neighborhood of Squirrel Hill, about 10 minutes from downtown Pittsburgh and the hub of Pittsburgh's Jewish community. The facade of the fortress-like concrete building is punctuated by rows of swirling, modernistic stained-glass windows illustrating the story of creation, the acceptance of God's law, the "life cycle" and "how human-beings should care for the earth and one another," according to its website. Among its treasures is a "Holocaust Torah," rescued from Czechoslovakia. 
 
 Its sanctuary can hold up to 1,250 people. 
 
 Eisenberg, the former synagogue president, said officials at Tree of Life had not gotten any threats that he knew of before the shooting. But he said security was a concern, and the synagogue had started working to improve it. 
 
 Chuck Diamond, a former rabbi at the synagogue who retired more than a year ago, said the building is locked during the week, and is outfitted with security cameras. "But on Sabbath it's an open door," he said. 
 
 "You know, you're always worried that something would happen," said Myron Snider, head of the cemetery committee for New Light Congregation, which meets at Tree of Life. Snider just got out of the hospital on Thursday and missed Saturday's service. 
 
 "But you never dream that it would happen like this," Snider added. "Just never ever dream that it would happen like this." 
 
 ___ 
 
 Associated Press writers Eric Tucker and Michael Balsamo in Washington, Claudia Lauer in Philadelphia, Gene Puskar in Pittsburgh, Marc Levy in Harrisburg and Allen G. Breed in Raleigh, N.C., and Michael Kunzelman in Silver Spring, Maryland, contributed to this report. 
 
 ___ 
 
 For AP's complete coverage of the Pittsburgh synagogue shootings: https://www.apnews.com/Shootings ||||| The FBI investigates after an active shooter situation at the Tree of Life Congregation on Saturday, Oct. 27, 2018, in the Squirrel Hill section of Pittsburgh. A shooter opened fire at the synagogue,... (Associated Press) 
 
 The FBI investigates after an active shooter situation at the Tree of Life Congregation on Saturday, Oct. 27, 2018, in the Squirrel Hill section of Pittsburgh. A shooter opened fire at the synagogue, killing multiple people and injuring others in one of the deadliest attacks on Jews in U.S. history.... (Associated Press) 
 
 PITTSBURGH (AP) — The Latest on a deadly shooting at a Pittsburgh synagogue (all times local): 
 
 7 a.m. 
 
 Police say the suspect in the deadly mass shooting at a Pittsburgh synagogue told officers that Jews were committing genocide and that he wanted them all to die. 
 
 Pittsburgh police said in an arrest affidavit made public early Sunday that Robert Gregory Bowers killed eight men and three women in the Tree of Life Synagogue before a tactical police team tracked him down and shot him. 
 
 A Pittsburgh police officer says in the warrant that Bowers was being treated for his injuries when he said Jews were "committing genocide to his people." 
 
 Bowers is charged with 11 counts of criminal homicide, six counts of aggravated assault and 13 counts of ethnic intimidation. 
 
 The police affidavit says calls began coming in to 911 just before 10 a.m. Saturday, reporting "they were being attacked." 
 
 ___ 
 
 12:30 a.m. 
 
 A gunman who expressed hatred of Jews exploited a vulnerability common in so many houses of worship across the country — doors that are unlocked for worship — to target a Pittsburgh synagogue. 
 
 Officials say Robert Bowers was armed with a rifle and three handguns when he walked inside the Tree of Life synagogue during Sabbath services Saturday morning and opened fire, killing 11 people and wounding six in what is believed to be the deadliest attack on Jews in U.S. history. 
 
 Police swarmed the building and traded gunfire with the gunman, who was shot multiple times but survived. 
 
 Four police officers are among the wounded. 
 
 Bowers faces 29 federal counts, including weapons offenses and hate crimes. 
 
 Law enforcement officials plan to discuss the massacre at a news conference Sunday morning. ||||| (CNN) Federal prosecutors have filed hate crime charges against a Pennsylvania man they say stormed a Pittsburgh synagogue and opened fire, killing 11 people. 
 
 Robert Bowers, 46, of suburban Baldwin, surrendered to authorities after Saturday morning's shooting at the Tree of Life synagogue. He made anti-Semitic statements during the shooting and targeted Jews on social media, according to a federal law enforcement official. 
 
 Bowers faces 29 charges in a rampage that left the historic Jewish neighborhood of Squirrel Hill and the rest of the nation stunned. The attack is believed to be the deadliest on the Jewish community in US history, the Anti-Defamation League said in a statement. 
 
 Police respond to the shooting Saturday at the Tree of Life synagogue in Pittsburgh. 
 
 "These incidents usually occur in other cities," Pittsburgh Public Safety Director Wendell Hissrich told reporters Saturday. "Today, the nightmare has hit home in the city of Pittsburgh." 
 
 Bowers is charged with 11 counts of using a firearm to commit murder and multiple counts of two hate crimes: obstruction of the exercise of religious beliefs resulting in death and obstruction of the exercise of religious beliefs resulting in bodily injury to a public safety officer, authorities said, citing a sealed criminal complaint. 
 
 "The crimes of violence are based upon the federal civil rights laws prohibiting hate crimes," said Scott Brady, US Attorney, and Bob Jones, the FBI special agent in charge of the Pittsburgh office, in a statement. 
 
 Bowers could face the death penalty if he is convicted of a hate crime. 
 
 Six people were injured as a result of the shooting, said Hissrich, four of whom were police officers who responded to the scene. No children were killed, he said. 
 
 "The actions of Robert Bowers represent the worst of humanity," Brady said. 
 
 Shots fired shortly before 10 a.m. 
 
 Saturday morning's violence rocked the city and the neighborhood surrounding the synagogue, which one congregant described as "close-knit." 
 
 Jim Waite, who lives across the street, said he walked outside after hearing a commotion. He assumed it was a car accident. A police car flew past him; another officer yelled to get inside. Waite said he then heard more than five -- possibly as many as nine -- shots. 
 
 JUST WATCHED Officer on dispatch audio: We need armor Replay More Videos ... MUST WATCH Officer on dispatch audio: We need armor 02:02 
 
 He said he could hear screams from inside the synagogue. 
 
 The Allegheny County emergency operations center received calls of an active shooter at 9:54 a.m., Hissrich told reporters. Officers were dispatched a minute later. 
 
 The suspect was in the process of leaving when he encountered a Pittsburgh police officer who "engaged him," Jones said. The officer was subsequently injured, and the suspect went back into the synagogue, where he hid from SWAT officers who arrived on the scene. 
 
 In all, two police officers and two SWAT officers were wounded in the confrontation, Hissrich said. Three of them were shot, according to the city's public safety department. 
 
 The suspect suffered multiple gunshot wounds and was in fair condition at a hospital. 
 
 Rapid reaction SWAT members leave the scene of the mass shooting on Saturday. 
 
 Investigators recovered a rifle and three handguns from the scene, Jones said. Authorities believe the suspect acted alone. Law enforcement had no knowledge of Bowers prior to the shooting, he said. 
 
 Five victims were being treated at two Pittsburgh hospitals, according to Paul Wood, a spokesman for University of Pittsburgh Medical Center. Four victims were being treated at UPMC Presbyterian, and one victim was being treated at UPMC Mercy. Another person was treated at Presbyterian and released. 
 
 Social media posts part of investigation 
 
 A law enforcement source told CNN that investigators believe an account on Gab, a social media platform, that espoused anti-Semitic views belonged to Bowers. 
 
 Its last ominous post was made at 9:49 a.m., just five minutes before police were notified of the shooting. 
 
 "I can't sit by and watch my people get slaughtered," Bowers wrote. "Screw your optics, I'm going in." 
 
 JUST WATCHED Synagogue shooting suspect targeted Jews online Replay More Videos ... MUST WATCH Synagogue shooting suspect targeted Jews online 02:13 
 
 Bowers' anti-Semitic comments also fueled other hate speech he shared on Gab, which has styled itself as an alternative to Twitter and puts nearly no restrictions on content. 
 
 In one post, Bowers claimed Jews were helping transport members of the migrant caravans. He believed that those in the migrant caravans were violent because they were attempting to leave countries that had high levels of violence. And Bowers repeatedly called them "invaders." 
 
 "I have noticed a change in people saying 'illegals' that now say 'invaders'," read one post six days before the shooting. "I like this." 
 
 Among the vitriolic statements is also criticism of President Donald Trump, who Bowers suggested was surrounded by too many Jewish people. 
 
 "Trump is surrounded by k****", "things will stay the course," read one post on Gab, using a derogatory term for Jews. 
 
 Roughly four hours before the shooting, Bowers commented in a post that he did not vote for Trump. 
 
 In a statement, Gab disavowed "all acts of terrorism and violence" and said its mission was "to defend free expression and individual liberty online for all people." 
 
 JUST WATCHED Investigators converge on suspect's home Replay More Videos ... MUST WATCH Investigators converge on suspect's home 02:22 
 
 After being alerted to the suspect's profile on the platform, Gab said it backed up the data, suspended the account and contacted the FBI. 
 
 Bowers also posted photos on his Gab account showing his handgun collection, including multiple magazines and sights. 
 
 On September 20, Bowers posted images of shooting targets he said were from July 2017. He said he was firing at the targets with a Walther PPQ handgun. 
 
 A law enforcement official familiar with the ongoing investigation told CNN that Bowers has a commercial driver's license and a history associated with the trucking industry. 
 
 Shooting 'more devastating than originally thought,' Trump says 
 
 The FBI will be the lead investigating agency, Hissrich said. 
 
 Trump told reporters at Joint Base Andrews in Maryland that the shooting was a "terrible, terrible thing." 
 
 "If there was an armed guard inside the temple, they would have been able to stop him," Trump said before boarding a flight to Indianapolis. 
 
 JUST WATCHED Trump: This attack is an assault on all of us Replay More Videos ... MUST WATCH Trump: This attack is an assault on all of us 02:33 
 
 After landing, he said, "We're learning a lot about it. It looks definitely like it's an anti-Semitic crime. And that is something you wouldn't believe could still be going on," he said. 
 
 Trump previously said in a tweet that the shooting was "far more devastating than originally thought." 
 
 The President ordered flags flown at half-staff in honor of the victims. 
 
 Security had been a 'major concern' 
 
 The Tree of Life synagogue is a Conservative Jewish congregation, according to its website. The synagogue has a Shabbat service at 9:45 a.m. Saturdays, the website said. 
 
 Conservative Judaism is one of the major denominations of the religion. The word "conservative" is not a political designation. 
 
 Michael Eisenberg, the immediate past president of the Tree of Life congregation, said three congregations -- Tree of Life, New Light and Dor Hadash -- would have been holding simultaneous services in the building on a typical Saturday. 
 
 A SWAT police officer and other first responders respond after a gunman opened fire at the synagogue. 
 
 There would usually would be about 40 people attending the Tree of Life service in the "main part of the building," Eisenberg said. In the basement below, New Light's service would also have about 30 to 40 people. And the Dor Hadash congregation in the rabbi's study room would have about 15 people, he said. 
 
 "On a day like today, the door is open," Eisenberg told CNN affiliate KDKA . "It's a religious service. You could walk in and out. Only on the high holidays is there a police presence at the entrance." 
 
 When he was the congregation's president, security was a "major concern," Eisenberg said. 
 
 The congregation had worked with the Department of Homeland Security to evaluate its exit routes, he said, and consulted a securities expert at the Jewish Federation about what to do in an active shooter situation. 
 
 "We were working with the other synagogues on what to do if something horrific like this happened," he said. 
 
 Just a few months ago, Tree of Life Rabbi Hazzan Jeffrey Myers addressed ongoing gun violence and lawmakers' failure to tackle the issue on the congregation's blog. 
 
 JUST WATCHED Official: One of the worst scenes I've seen Replay More Videos ... MUST WATCH Official: One of the worst scenes I've seen 01:11 
 
 In the July post, titled, "We Deserve Better," Myers said he was afraid school shootings would continue unless something changed in this year's mid-term elections 
 
 "Unless there is a dramatic turnaround in the mid-term elections, I fear ... the status quo will remain unchanged, and school shootings will resume. I shouldn't have to include in my daily morning prayers that God should watch over my wife and daughter, both teachers, and keep them safe," Myers wrote. "Where are our leaders?" 
 
 Anti-Semitic incidents in US surged in 2017 
 
 A number of other figures and organizations, such as the US Holocaust Memorial Museum, issued statements condemning the violence and extending its sympathy to the victims and their families. 
 
 An unidentified woman asks for a status update from firefighters a block away from the shooting. 
 
 "The museum reminds all Americans of the dangers of unchecked hatred and anti-Semitism which must be confronted wherever they appear and calls on all Americans to actively work to promote social solidarity and respect the dignity of all individuals," the Holocaust Museum said in a statement. 
 
 Pope Francis extended his condolences during a Sunday address, delivered in Italian from the window of the Apostolic Palace at the Vatican. 
 
 "May the most high welcome the deceased in his peace, comfort their families and sustain the injured," he said. "We are all wounded by this inhuman act of violence. May the Lord help us to end the outbreaks of hate that develop in our society, reinforcing a sense of humanity, respect for life, moral and civil values and a holy fear of God, who is love and father of all." 
 
 In 2017, anti-Semitic incidents in the United States surged nearly 60% , according to the Anti-Defamation League. It found 1,986 cases of harassment, vandalism or physical assault against Jews and Jewish institutions last year. 
 
 In a statement Saturday, the ADL said the attack was believed to be the deadliest on the Jewish community in US history. 
 
 "It is simply unconscionable for Jews to be targeted during worship on a Sabbath morning," it said, "and unthinkable that it would happen in the United States of America in this day and age." 
 
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 The Rabbinical Assembly said an act of hate against one community was an act of hate against all. 
 
 "This mass murder is a reminder that anti-Semitism is on the rise in America at a rate unprecedented in decades. This vicious hate crime, perpetrated against innocent people at prayer is but the latest in an escalating scourge of hate-based violence in America," it said in a statement. 
 
 The Orthodox Union and Rabbinical Council of America issued a joint statement expressing sympathy for the victims of the attack. 
 
 "This senseless act of anti-Semitic violence was not only an egregious attack on the Jewish community, but an attack on the very foundations of civil society and our collective democratic values," the Orthodox Union's executive vice president said.
– The Anti-Defamation League says the shooting at the Tree of Life synagogue in Pittsburgh is thought to be the deadliest attack specifically targeting Jews ever in the US—by far. CNN reports the previous attack to have that label occurred in 1985, when Seattle lawyer Charles Goldmark, his wife, and two sons were killed. (The Washington Post notes it "was actually a case of mistaken religious identity," as the family was not Jewish.) The toll in Saturday's shooting stands at 11. The AP reports police on Sunday said the victims were eight men and three women. In an arrest affidavit made public, police say that while treating alleged shooter Robert Gregory Bowers for injuries he sustained after being shot by police, he said Jews were "committing genocide to his people" and that he wanted them all to die. The AP separately reports on a "vulnerability" the shooter took advantage of: an unlocked door. While the Tree of Life synagogue required guests to ring a bell to gain access during the week, on the Jewish Sabbath the building was open to all guests for Shabbat services. The Post quotes the FBI special agent in charge as saying it was "the most horrific crime scene I’ve seen in 22 years." Federal hate crime charges were filed against Bowers on Saturday: 29 charges in all, including 11 counts of using a firearm to commit murder. The Pittsburgh Post-Gazette reports Pittsburgh police also filed charges on Saturday: 11 counts of criminal homicide, six counts of attempted homicide, six counts of aggravated assault, and 13 counts of ethnic intimidation. (Read what President Trump had to say about the shooting here.)