The suspect, who was in custody by noon, opened fire inside the Tree of Life Synagogue in the city's Squirrel Hill neighbourhood, according to The Associated Press.
The man accused of killing 11 people in a synagogue in Pittsburgh appeared in court today, two days after a massacre that tore through this community and set off new waves of fear and acrimony in the United States.
Robert Bowers, 46, had not been publicly seen since the bloodshed at the Tree of Life synagogue during Shabbat services.
Authorities said he stalked through the synagogue, gunning down 11 people before engaging in a gun battle with responding police officers while declaring that he wanted "to kill Jews".
Bowers, who police said had multiple gunshot wounds, was in hospital until today, not long before his court hearing.
As the Pittsburgh area prepares for a grim procession of funerals, investigators in the city and beyond have pored over Bowers's life, examining his actions leading up to the attack as well as his postings online.
The man authorities say carried out the deadliest attack on Jews in American history presented an unnerving paradox, offering an unremarkable public facade in person that contrasted with a raging online presence.
A social media account with Bowers' name repeatedly posted comments rife with anti-Semitism and other bigotry, but people who encountered him in person described him as an unremarkable loner who gave off no indications of that hatred.
People who knew him said he was a truck driver rarely seen socialising; high school classmates said they had no memories of him at all.
Bowers faces more than two dozen federal charges, including hate crime counts for which prosecutors say they hope to seek the death penalty. He also faces state charges, among them 11 counts of homicide.
During a court appearance just a few kilometres from the carnage-ridden synagogue, Bowers, seated in a wheelchair, was denied bail and only spoke to answer questions posed by the judge.
Federal marshals wheeled Bowers, wearing a blue sweatshirt and grey sweatpants, into the courtroom. He appeared coherent and aware of what was going on, answering "Yes" when the judge asked him his name and whether he had requested a public defender because he could not afford his own lawyer. When Magistrate Judge Robert Mitchell read the charges against him - including obstruction of exercise of religious belief resulting in death - and asked if Bowers understood them, he replied: "Yes sir."
Robert Bowers, the suspect in the deadly shooting at the Tree of Life Synagogue in Pittsburgh. Photo / AP
It did not appear that any friends or family of Bowers attended. Jon Pushinsky, 64, a member of one of the congregations that meets at Tree of Life, came to the court hearing in a show of strength on its behalf after the attack.
"It was important to be here to show our congregation remains strong and will stand up, even in the face of evil," he said.
Scott Brady, the US Attorney for the Western District of Pennsylvania, has begun the process of seeking the death penalty in the case, a decision that rests with the attorney-general. Speaking after the hearing, he told reporters: "Rest assured, we have a team of prosecutors working hard to ensure that justice is done."
Even as the criminal case against Bowers was beginning in the court system, people in grief-stricken Pittsburgh began moving towards burying those who were killed and reeling from the rampage.
Funerals were scheduled to begin tomorrow for the victims, which included a 97-year-old woman, a husband and wife and two brothers. Vigils were also expected to continue as people grappled with still another horror in a seemingly safe public place.
The sense of community gave way to still more rancor that stretched to Washington and beyond. More than 30,000 people signed an open letter to President Donald Trump from leaders of a Pittsburgh-based Jewish group saying he would not be welcome unless he denounced white nationalism and "stop targeting and endangering all minorities".
No @PressSec, CNN did not say @realDonaldTrump was directly responsible for the bomb sent to our office by his ardent and emboldened supporter. We did say that he, and you, should understand your words matter. Every single one of them. But so far, you don’t seem to get that. pic.twitter.com/ZbH5DQggWq
Trump, who has a lengthy history of incendiary rhetoric towards minorities that has continued since taking office, condemned the synagogue shooting as "pure evil" and denounced anti-Semitism.
He also suggested that the synagogue should have had armed guards, something he has said after other mass shootings. Trump has continued to lash out at news organisations since the shooting, describing the media as being responsible for "great anger in our Country," comments he made the same day a third suspected explosive device was delivered to CNN in less than a week.
While the White House and Trump's allies have sought to push back against suggestions his rhetoric has contributed to the country's spasms of violence, a grieving Rabbi Jeffrey Myers directly linked the massacre at his Tree of Life synagogue to the rhetoric of US politicians.
"It starts with speech," Myers said to loud applause at a vigil attended by two US senators. "It has to start with you as our leaders. My words are not intended as political fodder. I address all equally. Stop the words of hate."
Leader of Islamic Center of Pittsburgh announces Muslim community has raised more than $70,000 for synagogue attack victims and their families.
"We just want to know what you need ... If it's people outside your next service protecting you, let us know. We'll be there." pic.twitter.com/D2UyNzBFHx
White House press secretary Sarah Sanders said Trump and first lady Melania Trump planned to visit Pennsylvania tomorrow to "express the support of the American people and grieve with Pittsburgh community."
Sanders, who called the shooting "an act of evil," Sanders also defended Trump amid criticism that he has stoked divisions by refusing to tone down his rhetoric in the wake of the shooting and last week's mail bombs that targeted the President's critics.
"The very first thing that the President did was to condemn the attacks, both in Pittsburgh and in the pipe bombs," Sanders said.
