PITTSBURGH (AP) — A gunman who’s believed to have spewed anti-Semitic slurs and rhetoric on social media barged into a baby-naming ceremony at 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 at least 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 expected to face federal hate-crime charges.

“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 late-afternoon news conference, characterizing the slaughter as a “terrible and unspeakable act of hate.”

The shooting came amid a rash of high-profile attacks in an increasingly divided country, including the series of pipe bombs mailed over the past week to prominent Democrats and former officials.

The shooting 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.”

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.

The social media site Gab.com said the alleged shooter had a profile on its website, which is popular with far-right extremists. The company said the account was verified after the shooting and matched the name of the gunman.

A man with the same name posted on Gab before the shooting 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.

Bowers also recently posted a photo of a collection of three semi-automatic handguns he titled “my glock family,” a reference to the firearms manufacturer. He also posted photos of bullet holes in person-sized targets at a firing range, touting the “amazing trigger” on a handgun he was offering for sale.

The attack took place during a baby-naming ceremony, according to Pennsylvania Attorney General Josh Shapiro. During a Jewish baby naming ceremony, the baby is given his or her Hebrew name. The name could be a name that sounds like the baby’s secular name or has significance in his or her family’s history.

Officials later said that no children were hurt.

“It is a very horrific crime scene. It’s one of the worst that I’ve seen and I’ve been on some plane crashes,” said a visibly moved Wendell Hissrich, the Pittsburgh public safety director.

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.

Jonathan Greenblatt, chief executive officer of the Anti-Defamation League, said the group believes it is the deadliest attack 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.”

World Jewish Congress President Ronald S. Lauder called the shooting “an attack not just on the Jewish community, but on America as a whole.”

Trump called the shooting a “wicked act of mass murder” that “is pure evil, hard to believe and frankly something that is unimaginable.”

Trump has at times been accused by critics of failing to adequately condemn hate, such as when he blamed “both sides” for the violence at a Charlottesville white supremacist rally.

On Saturday, he said that anti-Semitism “must be confronted anywhere and everywhere it appears.”

The synagogue is a fortress-like concrete building, its facade 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.

Michael Eisenberg, the immediate past president of the Tree of Life Synagogue, lives about a block from the building.

He was getting ready for services when he received a phone call from a member who works with Pittsburgh’s Emergency Services, saying he had been notified through a scanner and other communications that there was an active shooter at their synagogue.

“I ran out of the house without changing and I saw the street blocked with police cars. It was a surreal scene. And someone yelled, ‘Get out of here.’ I realized it was a police officer along the side of the house. ... I am sure I know all of the people, all of the fatalities. I am just waiting to see,” Eisenberg said.

He said officials at the synagogue had not gotten any threats that he knew of prior to the shooting. The synagogue maintenance employees had recently checked all of the emergency exits and doors to make sure they were cleared and working.

“I spoke to a maintenance person who was in the building and heard the shots. He was able to escape through one of the side exit doors we had made sure was functioning,” Eisenberg said.

Eisenberg said the larger main synagogue, Tree of Life, had let two other smaller congregations use space at the synagogue on Saturdays, and that all three were meeting at the time.

Jeff Finkelstein of the Jewish Federation of Greater Pittsburgh said local synagogues have done “lots of training on things like active shooters, and we’ve looked at hardening facilities as much as possible.”

“This should not be happening, period,” he told reporters at the scene. “This should not be happening in a synagogue.”

Just three days before the shooting, Rabbi Jeffrey Myers posted a column on the congregation’s website, noting that people make time to attend funerals, but not for life’s happy occasions.

“There is a story told in the Talmud of a wedding procession and a funeral procession heading along parallel roads, with the roads intersecting,” Myers wrote on Wednesday. “The question asked is: when they meet at the fork, which procession goes first, funeral or wedding? The correct answer is wedding, as the joy of the couple takes precedence. In fact, the funeral procession is to move out of sight so that their joy is not lessened.”

Myers ended his column with words that now seem all too prescient.

“We value joy so much in Judaism that upon taking our leave from a funeral or a shiva house, the customary statement one makes (in Yiddish) is ‘nor oyf simches’ - only for s’machot,” Myers wrote. “While death is inevitable and a part of life, we still take our leave with the best possible blessing, to meet at joyous events. And so I say to you: nor oyf simches!”

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