People mourn the loss of life as they hold a vigil for the victims of Pittsburgh synagogue shooting in Pittsburgh, Pennsylvania, US, October 27, 2018. /Reuters Photo
Federal investigators said they are treating the shooting as a hate crime.
Bowers' social media posts are reportedly rife with anti-Semitic contents.
He reportedly shouted "All Jews must die" as he stormed the synagogue with an assault rifle and at least three handguns.
Investigators believed the gunman was acting alone but his full motive was not immediately clear, said Bob Jones, the special agent in charge of the FBI's office in Pittsburgh at a press conference.
In the wake of the fatal shooting, US President Donald Trump denounced the "evil Anti-Semitic attack," saying it's "an assault on humanity." He said he will travel to Pittsburgh.