(CNN) The American Jewish community is in mourning after a gunman killed 11 worshippers Saturday morning in a Pittsburgh synagogue in the deadliest attack ever on Jews in the United States.

Jewish organizations said the violence at Tree of Life synagogue underscored the dangers of unchecked hatred in a time when anti-Semitic acts are on the rise.

According to law enforcement, suspect Robert Bowers targeted Jews online and made anti-Semitic comments during the shooting. While receiving medical care, he told a SWAT officer that he wanted all Jews to die, according to a criminal complaint.

Bowers, whom authorities believe acted alone, faces 29 federal charges, some of which are punishable by death. The US attorney in Pittsburgh, Scott Brady, is seeking approval from Attorney General Jeff Sessions to seek the death penalty against Bowers, according to a Justice Department spokesman.

Bowers is scheduled to make his first court appearance on Monday afternoon.

The shooting struck the heart of Pittsburgh's historically Jewish Squirrel Hill neighborhood and reverberated across the United States, closing out a week of traumatic events with common roots in hate. President Donald Trump ordered flags flown at half-staff in honor of the victims.

On Sunday, visiting dignitaries joined community leaders, politicians and residents of the metropolitan Pittsburgh area at the University of Pittsburgh for an interfaith service. They pledged to support the community and fight hate speech.

"We will drive anti-Semitism and the hate of any people back to the basement, on their computer, and away from the open discussions and dialogues around this city, around this state and around this country," Pittsburgh Mayor Bill Peduto said.

A trail of hate leads to suspect

Sunday's vigil, the second since the Saturday morning shooting, came as a fuller picture began to emerge of the suspect. The 46-year-old resident of suburban Baldwin was taken into custody after a shootout with police. He is being treated in a hospital for gunshot wounds.

"They're committing genocide to my people," Bowers told police during the shootout, according to an FBI affidavit. "I just want to kill Jews."

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Investigators searched Bowers' home with a robot on Saturday and searched his vehicle on Sunday, the FBI said. They're looking for surveillance footage from the area that could provide clues.

For weeks before the shooting, Bowers targeted Jews in frequent posts on Gab, a social media platform that bills itself as "the free speech social network." He used anti-Semitic slurs, complained that President Donald Trump was surrounded by too many Jewish people and blamed Jews for helping migrant caravans in Central America.

He also posted pictures of his handgun collection. Bowers has 21 guns registered to his name, said Rep. Mike Doyle, whose district includes Squirrel Hill.

Four hours before the shooting, Bowers posted about Trump. Minutes before storming inside the building, he logged onto Gab again and wrote to his followers.

"I can't sit by and watch my people get slaughtered," he wrote. "Screw your optics, I'm going in."

Gab denied supporting violence and said its mission is "to defend free expression and individual liberty online for all people." Gab said it has backed up the suspect's profile data, suspended the account and contacted the FBI.

The victims have been identified

Robert Jones, the FBI special agent in charge of the Pittsburgh office, called the shooting "the most horrific crime scene" he'd witnessed in 22 years with bureau. It began as a peaceful morning as dozens of people filed inside the building to celebrate Shabbat services with three congregations, Tree of Life, Dor Hadash and New Light.

Rabbi Hazzan Jeffrey Myers with Tree of Life said the shooting began shortly after he started services at 9:45 a.m.

"My holy place has been defiled," he said at Sunday's service. He vowed to rebuild his congregation and called on those in the audience to do their part.

"Words of hate are unwelcome in Pittsburgh. It starts with everyone in this room, and I want to address for a moment some of our political leaders who are here. Ladies and gentlemen, it has to start with you as our leaders," he said to a standing ovation.

"My words are not intended as political fodder, I address all equally. Stop the words of hate."

Authorities on Sunday released the names of the 11 victims, all of whom were from Pennsylvania. They included a married couple, a pair of brothers and a beloved physician.

Joyce Fienberg, 75, Rose Mallinger, 97, Jerry Rabinowitz, 66, Cecil Rosenthal, 59, David Rosenthal, 54, Daniel Stein, 71, Melvin Wax, 87, and Irving Younger, 69, were from Pittsburgh. Richard Gottfried, 65, was from Ross Township and Bernice Simon, 84, and Sylvan Simon, 86, were from Wilkinsburg, Allegheny County Chief Medical Examiner Karl Williams said.

The Allegheny County medical examiner's office said late Sunday that autopsies had been completed on the victims and all 11 died from rifle wounds with several suffering head wounds.

Six more people were injured: two police officers, two SWAT officers and two others, Pittsburgh Public Safety Director Wendell Hissrich said. Bowers shot three of them, authorities said.

Five people were hospitalized, including the four officers. Two were in critical condition: a 55-year-old man with multiple injuries to his extremities, and a 70-year-old man with gunshot wounds to the torso.

One officer was released Saturday and three remain in the hospital. All four were "in good spirits" when visited by a union representative on Saturday, said Robert Swartzwelder, president of the Pittsburgh Fraternal Order of Police.

Shootout ends in surrender

Squirrel Hill residents heard screams and gunshots coming from the synagogue. In minutes, police officers in tactical gear arrived and urged them to stay indoors.

Police said they received 911 calls about an active shooter around 10 a.m., five minutes after Bowers made his last social media post. When officers entered the building, they found the victims' bodies and survivors hiding. They rescued at least two people from the basement and scrambled to evacuate people as they looked for the gunman.

Tree of Life Synagogue in the Squirrel Hill neighborhood following the shoooting.

Two officers encountered the gunman as he was attempting to leave the building, according to a criminal complaint. The gunman fired at them, shooting one officer in the hand before fleeing back inside the synagogue. The other officer suffered several cuts to his face from shrapnel and broken glass.

SWAT officers found Bowers on the third floor of the building and exchanged gunfire with him until he surrendered, authorities said. Two SWAT officers were injured in the gunfight, along with Bowers.

Bowers used a Colt AR-15 rifle and three Glock .357 handguns during the attack, police said. Bowers legally purchased the three Glock .357s, a law enforcement official familiar with the investigation told CNN. It's not clear whether the AR-15 was purchased legally.

In addition to those four guns, investigators recovered a shotgun in the alleged shooter's car that was not used in the shooting, Doyle said, referencing information he learned from law enforcement briefings.

Suspect could face the death penalty

Bowers faces at least 29 federal charges, including 11 counts of obstruction of exercise of religious beliefs resulting in death, plus 11 counts of using a firearm to commit murder. A conviction on any could be punishable by death, US Attorney Brady said.

When asked if the shooting could be considered an instance of domestic terrorism, Brady said there would need to be evidence the suspect tried to propagate a particular ideology through violence.

"We continue to see where that line is. But for now, at this point in our investigation, we're treating it as a hate crime."

In the shootout with police, Bowers also faces four counts of obstruction of exercise of religious beliefs resulting in bodily injury to a public safety officer, and three counts of use and discharge of a firearm during and in relation to a crime of violence.

He was also charged with 11 state offenses, including attempted homicide and aggravated assault.

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The United States Holocaust Memorial Museum said the shooting is a reminder of "all the dangers of unchecked hatred and anti-Semitism, which must be confronted wherever they appear."

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.

The shooting drew sympathy from the Israeli government and its people. Mourners staged makeshift memorials in Jerusalem's Zion Square and Israeli Prime Minister Benjamin Netanyahu spoke on the phone with Pennsylvania Gov. Tom Wolf on Sunday to express his condolences. Israeli Diaspora Affairs Minister Naftali Bennett traveled to Pittsburgh for Sunday's service.

"Nearly 80 years since Kristallnacht, when the Jews of Europe perished in the flames of their houses of worship, one thing is clear: Anti-Semitism, Jew-hating, is not a distant memory," Bennett said. "It's not a thing of the past, nor a chapter in the history books. It is a very real threat."

Adam Hertzman, director of marketing for the Jewish Federation of Pittsburgh, said it was too early to say if the community will add permanent security to synagogues in the area.

"Our focus at the moment is on mourning those who have passed and trying to comfort the people who are bereaved," Hertzman said.

CORRECTION: This story has been updated to give the correct age for Melvin Wax. He was 87.