ROUGH CUT (NO REPORTER NARRATION) A gunman yelling, "All Jews must die," stormed a Pittsburgh synagogue during Saturday services, killing 11 worshippers and wounding six other people including four police officers, before he was arrested.

U.S. attorney for western Pennsylvania Scott Brady told a news conference that charges could be filed later on Saturday against the suspected shooter, 46-year-old Robert Bowers from Pittsburgh.

"The actions of Robert Bowers represent the worst of humanity.

We are dedicating the entire resources of my office to this federal hate crime investigation and prosecution," Brady said.

"Please know that justice in this case will be swift and it will be severe." FBI special agent Bob Jones said the Federal Bureau of Investigation, which is leading the probe into the attack, believed Bowers was acting alone, adding: "We have no knowledge that he was known to law enforcement before today." KDKA television cited police sources as saying Bowers walked into the building and yelled "All Jews must die." Bowers was in a hospital in fair condition with multiple gunshot wounds.

Patients at area hospitals included a 61-year-old woman, a 70-year-old man, and a 55-year-old officer.

No children were killed, authorities said.

Three police officers were shot and one was injured by shrapnel, authorities said.

Two of the six people injured were in critical condition.