Mourners react during a memorial service at the Sailors and Soldiers Memorial Hall of the University of Pittsburgh, a day after 11 worshippers were shot dead at a Jewish synagogue in Pittsburgh, Pennsylvania, US, October 28, 2018. REUTERS/Cathal McNaughton.

The man charged with shooting 11 worshippers to death at a Pittsburgh synagogue, marking the deadliest ever attack on America’s Jewish community, was due to make his first court appearance on Monday before a federal judge.

Robert Bowers, 46, who has a history of posting antisemitic material online, has been charged with 29 criminal counts, including the violation of US civil rights laws in what federal prosecutors say was a hate crime.

Several of the charges can be punishable by the death penalty.

Bowers is accused of storming into the Tree of Life temple in Squirrel Hill, the heart of Pittsburgh’s close-knit Jewish community, yelling “All Jews must die” as he opened fire on members of three congregations holding Sabbath prayer services there on Saturday morning.

In addition to the 11 mostly elderly worshippers who were killed, six people, including four police officers who confronted the gunman, were wounded before the suspect surrendered. Two of the surviving victims remain hospitalized in critical condition.

“The fact that this attack took place during a worship service makes it even more heinous,” US Attorney Scott Brady said on Sunday at a news conference.

Bowers’ initial appearance before a judge was scheduled for Monday afternoon in US District Court in Pittsburgh, Brady said.

About 2,500 people attended an interfaith memorial service for the victims that was held late on Sunday on the University of Pittsburgh campus.

The dead included two brothers in their 50s, David and Cecil Rosenthal, a married couple in their 80s, Sylvan and Bernice Simon, and 97-year-old Rose Mallinger, the oldest of the victims.

Another was Dr. Jerry Rabinowitz, 66, a family physician who initially escaped the attack only to be killed when he returned to render aid to the wounded, according to a Wall Street Journal op-ed column by Pittsburgh carpet salesman Lou Weiss, who knew five of the victims personally.

The killings rocked the Squirrel Hill community, an enclave that encompasses several synagogues and Jewish religious schools, and sparked security alerts at places of worship across the country.

The massacre also took on political overtones as some complained that the confrontational, nationalistic rhetoric of US President Donald Trump has encouraged right-wing extremists and fed a surge in activity by hate groups.

Trump branded Saturday’s shooting an act of pure evil and called on Americans to rise above hatred.