The alleged gunman who killed 11 people and injured six at a Pittsburgh synagogue on Saturday assailed the Jewish resettlement agency HIAS on his web page and said “I’m going in.”

The shooting occurred shortly before 10 a.m. during a circumcision ceremony at The Tree of Life, a 150-year-old Conservative movement congregation in the Squirrel Hill neighbourhood, which has a substantial Jewish population. Some 100 worshippers were at the synagogue, which was holding three services at the time.

Police arrived on the scene just minutes after receiving calls about the gunfire and engaged the suspect, who has been identified as Robert Bowers, a 46-year-old white male. Bowers shouted “All these Jews need to die,” according to reports.

Among the injured were a 70-year-old male and a 61-year-old woman. The man had injuries to his torso and was in critical condition. Four police offers were wounded.

Pittsburgh Public Safety Director Wendell Hissrich called the attack a hate crime, which puts it under the purview of the FBI.

Bob Jones, the FBI official from the Pittsburgh office in charge of the bureau’s investigation, at a late afternoon news briefing called it the ‘most horrific crime scene” he has seen in his 22 years with the FBI.

Bowers surrendered to a SWAT team on the scene. He allegedly was carrying an assault-style rifle and multiple pistols, a law enforcement official said. The suspect was taken to a hospital, Hissrich said, but did not offer details.

On screen shots from his suspended web page on gab.com, Bowers wrote:

“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,” he wrote.

The page also said that “jews are the children of satan. (john 8:44)”

Bowers’ account was rife with anti-Semitic conspiracies and anti-Trump posts/conspiracies.

Jason Lando, a police spokesman, told CNN that neighbours were told to keep indoors and shelter in place. Carnegie Mellon University also was put on lockdown.

Police said that at least three officers were hit in the gunfire exchanges.

Prime Minister Justin Trudeau said on Twitter: “Canadians’ hearts are with the Jewish community in Pittsburgh today, as they endured a horrific anti-Semitic attack while at prayer.”

Minister of Foreign Affairs, Chrystia Freeland tweeted: “Horrified by the mass shooting at a synagogue in #Pittsburgh today. My heart goes out to all those affected. We must stand together against hatred, intolerance, antisemitism, and violence.”

U.S. President Donald Trump responded to the shooting on Twitter, saying that it “looks like multiple fatalities.”

“Watching the events unfolding in Pittsburgh, Pennsylvania,” Trump said. “Law enforcement on the scene. People in Squirrel Hill area should remain sheltered.”

Later Trump told reporters: “This is a case where if they had an armed guard inside, they might have been able to stop him immediately” and “maybe there would be nobody killed.”

Tree of Life, which merged five years ago with another congregation, Ohr L’Simcha, is on the same campus as two other synagogues: New Light, which is also Conservative, and Dor Hadash, a Reconstructionist synagogue.

The New York Police Department deployed extra officers to that city’s synagogues on Saturday morning.

In Israel, Prime Minister Benjamin Netanyahu in a videotaped statement said that he was “heartbroken and appalled by the murderous attack” on the Tree of Life synagogue.

“The entire people of Israel grieve with the families of the dead. We stand together with the Jewish community of Pittsburgh,” he said. “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.

Israeli President Reuven Rivlin said in a statement that “We are thinking of our brothers and sisters, the whole house of Israel, in this time of trouble, as we say in the morning prayers. We are thinking of the families of those who were murdered and praying for the quick recovery of those who were injured. I am sure that the law enforcement agencies and the legal authourities in the U.S. will investigate this horrific event thoroughly and that justice will be served on the despicable murderer.”

Israel’s Education Minister Naftali Bennett, who also serves as the country’s Diaspora minister, left for Pittsburgh on Saturday night in Israel shortly after news of the shooting. He will visit the synagogue, meet with the local Jewish community and participate in the funerals of those killed in the attack, a statement from his office said.

“When Jews are murdered in Pittsburgh, the people of Israel feel pain,” Bennett said. “All Israel are responsible for one another.”

He also said that “Jewish blood is not free. I am going to offer strength to the community and its leaders, and to examine how we can offer assistance.”