The man arrested over the mass shooting at a Pittsburgh synagogue later told police that Jews were “committing genocide to his people” and he wanted them all to die.

Robert Gregory Bowers is charged with killing eight men and three women inside the Tree of Life Synagogue on Saturday before a tactical police team tracked him down and shot him, authorities said in state and federal affidavits.

“I just want to kill Jews,” Bowers told an officer, according to one of the documents.

A pair of brothers and a married couple were among his victims, the oldest of whom was a 97 year old who attended the synagogue with her daughter, Karl Williams, chief medical examiner for Allegheny County, told reporters on Monday morning (AEST).  

Dr Williams listed the 11 victims as: Joyce Fienberg, 75; Richard Gottfried, 65, Rose Mallinger, 97; Jerry Rabinowitz, 66; Cecil Rosenthal, 59, and his brother David Rosenthal, 54; married couple Bernice Simon, 84, and Sylvan Simon, 86; Daniel Stein, 71; Melvin Wax, 88; and Irving Younger, 69.

The shooting has been labelled the deadliest attack on Jewish people in American history by the leader of the Anti-Defamation League.

Federal prosecutors have charged suspected gunman Robert Gregory Bowers, who was armed with an AR-15 rifle and three handguns and used all four weapons in the attack, with hate crimes but not domestic terrorism.

The charges laid included 11 state counts of criminal homicide, six counts of aggravated assault and 13 counts of ethnic intimidation.

Pittsburgh police released this picture of suspect Robert Bowers.

The 46-year-old Pittsburgh man was also charged in a 29-count federal criminal complaint that included counts of obstructing the free exercise of religious beliefs resulting in death – a federal hate crime – and using a firearm to commit murder.

“A hate crime is where an individual is animated by a hatred or certain animus toward a person of a certain ethnicity or religious faith,” US Attorney Scott Brady said.

“It becomes domestic terrorism where there’s an ideology that that person is then also trying to propagate through violence. We continue to see where that line is. But for now, at this place in our investigation, we’re treating it as a hate crime and charging it as such,” he explained.

US Attorney General Jeff Sessions said the charges “could lead to the death penalty”.

Bowers is in a stable condition after he was shot by authorities as he fled the synagogue.

Calls began coming in to 911 from the synagogue just before 10am on Saturday.

Bowers shot one of the first two officers to respond in the hand, and the other was wounded by “shrapnel and broken glass”, according to court documents.

A tactical team found Bowers on the third floor, where he shot two officers multiple times, an affidavit said.

One of the wounded officers was treated and released, and a second was expected to be released on Sunday. The other two were expected to remain in hospital.

Two other people in the synagogue, a man and a woman, were wounded by Bowers and were in stable condition, court documents said.

Thousands gathered for a vigil on Saturday night. Photo: Getty

The nation’s latest mass shooting drew condemnation and expressions of sympathy from politicians and religious leaders of all stripes. With the midterm election just over a week away, it also reignited a longstanding and bitter debate over guns.

Pope Francis led prayers for Pittsburgh on Sunday in St Peter’s Square.

Calling the shooting an “evil anti-Semitic attack”, US president Donald Trump ordered flags at federal buildings throughout the US to be flown at half-mast. He said he planned to travel to Pittsburgh, but offered no details.

-with AAP