"He gets up in the morning with new and inventive ways to divide us", US Rep. Adam Schiff, a California Democrat who is Jewish, said on CNN's "State of the Union" broadcast on October 28.
Earlier, U.S. Attorney General Jeff Sessions said federal prosecutors could seek the death penalty.
Bowers killed eight men and three women before a tactical police team tracked him down and shot him, authorities said.
Neighbours speaking to USA media describe Robert Bowers as "normal". The Allegheny County District Attorney's office filed charges that include multiple charges of homicide, aggravated assault and ethnic intimidation.
Though Bowers hid his anti-Semitic rage from his neighbors, it was on full display online.
A crowdfunding campaign called Muslims Unite for Pittsburgh Synagogue raised more than $90,000 for survivors and families, while a fundraiser led by a graduate student in Washington had taken in almost $545,000 as of Monday morning, with funds to go to the congregation.
Robert Gregory Bowers, who was wounded in a gun battle with police during the shooting rampage, was released from a hospital in the morning and a few hours later was wheeled into the courtroom, where he was ordered held without bail for a preliminary hearing on Thursday, when prosecutors will outline their case against him. They were both killed by the shooter. The local medical examiner, Dr. Karl Williams, said, "Lots of shots were fired, there were casings everywhere".
The attack, the deadliest on Jews in USA history, targeted a synagogue that is an anchor of Pittsburgh's large Jewish community, about a 25-minute drive from Bowers's home. "You yourself called the murderer evil, but yesterday's violence is the direct culmination of your influence", the open letter said. It breaks my heart'.
Gideon Murphy places a flower at the Tree of Life Synagogue in Pittsburgh, Sunday, Oct. 28, 2018.
Yesterday morning, death and violence entered a house of worship.
World leaders denounced the attack, deploring it as an affront to humanity.
The synagogue massacre has heightened debate over the rhetoric US President Donald Trump uses with critics saying it has encouraged right-wing extremism, which the administration rejects. "During increasingly polarised times for all faiths, we stand in solidarity with a religious community we have always viewed as our elder brothers and sisters". The Johns Hopkins School of Advanced International Studies student says the funds will go directly to the Tree of Life congregation. "Are we going to keep on living like this, barricaded?"
"I heard the gunfire getting louder, and I knew that with the length of the sanctuary, I wasn't able to run there and take care of them, because in hindsight, I would have been the eighth casualty". "For us that is not a lovely theory but a lived reality".
Vice President Mike Pence was joined by a Jews for Jesus "rabbi" who prayed for the victims of the Pittsburgh synagogue shooting at a Republican campaign rally in MI on Monday. He prayed "to help us to extinguish the flames of hatred that develop in our societies".
Pope Francis led prayers for Pittsburgh on Sunday in St. Peter's Square.