Police say 46-year-old Robert Bowers was armed with an assault rifle and three handguns when he opened fire at a Pittsburgh synagogue Saturday morning, killing 11 people and injuring six, including four police officers.

Investigators say Bowers entered the Tree of Life synagogue in Squirrel Hill just before 10 a.m. and started shooting. The attack lasted 20 minutes.

Two of the injured victims are in critical condition. No children were injured in the attack.

Investigators are expected to release the names of the victims Sunday morning.

Police are investigating the shooting as a hate crime. 

Bowers allegedly made anti-Semitic comments during the attack. Police said Bowers was taken to a hospital with multiple gunshot wounds.

Investigators searched his home and are looking at his social media accounts, which they said have messages targeting Jews and show photos of guns.

Bowers is facing 29 federal charges, including 11 counts of using a firearm to commit murder. He could face the death penalty.