“And in the aftermath of this tragedy, we must come together and take action to prevent these tragedies in the future. We cannot accept this violence as normal,” he added.

Former President Barack Obama also called for action, writing on Twitter, “We have to stop making it so easy for those who want to harm the innocent to get their hands on a gun.”

Several news outlets have identified the gunman as 46-year-old Robert Bowers, who is currently receiving medical treatment for multiple gunshot wounds.

He appears to be strongly anti-Semitic. Law enforcement sources told KDKA that Bowers walked into the synagogue and yelled, “All Jews must die,” before opening fire.

The gunman had an assault-style rifle and at least three handguns with him at the synagogue, according to Bob Jones, the FBI special agent in charge of the Pittsburgh field office.