"The approach we need to be looking at is how we take the guns - the common denominator of every mass shooting in America - out of the hands of those looking to express hatred through murder," Peduto told reporters.
The shooter targeted a congregation that is an anchor of Pittsburgh's large and close-knit Jewish community, a massacre that authorities immediately labelled a hate crime as they investigated the suspect's history of anti-Semitic online screeds.
A man with Bowers' name had posted anti-Semitic statements on social media before the shooting, expressing anger that a nonprofit Jewish organisation in the neighbourhood has helped refugees settle in the US. In what appeared to be his final social media post hours before the attack, the man wrote: "I can't sit by and watch my people get slaughtered. Screw your optics, I'm going in."
The FBI said Bowers was not previously known to law enforcement before he drove to the synagogue, as three different congregations celebrated the Jewish Sabbath inside.
He allegedly walked through an unlocked door armed with a Colt AR-15 rifle and three Glock .357 pistols - all four of which fired, police said, as he moved around the large building, screaming about Jews.
"There were casings everywhere," said Allegheny County chief medical examiner Karl Williams, whose team spent yesterday inside the synagogue identifying the dead.
"This is the most horrific crime scene I've seen in 22 years with the Federal Bureau of Investigation," said Robert Jones, the FBI special agent in charge of the case.
The three men and eight women killed include Rose Mallinger, a 97-year-old resident of the neighbourhood; and Cecil and David Rosenthal, two brothers in their 50s and the youngest of the victims; and Bernice Simon and her husband Sylvan, both in their 80s. Also killed were Joyce Fienberg, 75; Richard Gottfried, 65; Jerry Rabinowitz, 66; Daniel Stein, 71; Melvin Wax, 88; and Irving Younger, 69.
Two other worshipers were wounded in the initial shooting spree, which might have lasted about 15 minutes.
Two police officers arrived 10 minutes after the shooting started, and stopped the gunman near the synagogue's entrance.
"He had finished and he was exited the building," Jones told reporters. "Had Bowers made it out of that facility, there is a strong possibility that additional violence would have occurred."
Instead, authorities say, Bowers exchanged gunfire with the two officers, shooting one in the hand and injuring another with shrapnel. He allegedly fled back inside the synagogue, and a small SWAT team assembled to pursue him and try to rescue the wounded inside.
Bowers shot two more officers multiple times during a brief standoff on the building's third floor, according to criminal complaints. The final toll was 11 people killed and six wounded, including the four officers.
The suspect was also shot several times himself before he finally surrendered. He remained in fair condition and under federal custody today.
Two of the wounded officers remained in stable condition in a hospital. As they recovered, Jewish leaders along with local, state and federal officials detailed what happened in the shooting's aftermath, and what is still to come.
Authorities have closed off the synagogue and much of the surrounding area, and worked to identify the bodies and process what Jones called "a large and complex crime scene."
As news of the shooting spread, police locked down nearby synagogues in the heavily Jewish neighbourhood. "It could have just as easily been our congregation," said Rabbi Aaron Bisno of nearby Rodef Shalom. "We don't know what motivated the shooter, but when something like this strikes, the randomness of it terrifies."
Police also raced to synagogues in Washington, New York City, Chicago and Los Angeles to provide additional security.
Meanwhile, Bowers's home and car was were due to be searched, and investigators have begun to scour his reportedly extensive social media feeds. These may include a since-deleted Gab account in which a user with Bowers's name compared Jews to Satan and complained that President Trump's "Make America Great Again" movement cannot succeed so long as Jews "infest" the country.
Investigators have not said what their searches have revealed, but they do not believe the suspect had accomplices.
Bowers is expected to have his first court hearing on Monday. He faces at least 23 state charges, including homicide, attempted homicide and aggravated assault against police officers. He faces an additional 29 federal charges accusing him of civil rights and hate crimes.
"This was the single most lethal and violent attack on the Jewish community in the history of the country," said Jonathan Greenblatt, CEO and national director of the Anti-Defamation League. "We've never had an attack of such depravity where so many people were killed."
Coming less than two weeks before a midterm election and hours after a man was arrested and accused of mailing pipe bombs to prominent Democrats, the Pittsburgh massacre is likely to intensify a national debate over bigotry and hatred in American politics - not to mention gun control.
Anti-Semitic incidents rose more than 50 percent in 2017, according to the ADL, with nearly 2,000 documented events. The previous deadliest anti-Semitic attack, the group said, was a case of mistaken religious identity that killed four non-Jews in 1985.
While it anti-Semitic nature is uniquely horrifying, the Pittsburgh massacre is only the latest of many mass casualty events that take place more frequently in the United States than almost every other nation in the world.
Once again the suspect was a man armed with a semiautomatic assault-style weapon - as was, for example, the gunman who killed 49 people in Orlando's Pulse nightclub in 2016. Once again the crime scene was a house of worship, a classic "soft target," as was the First Baptist Church in Sutherland Springs, Tex., where a disturbed gunman hoping to kill his mother-in-law slaughtered 26 people during a Sunday service last November.
And once again the victims were members of an ethnic or religious minority with a long history of persecution - as were the nine African American worshipers killed three years ago when a white supremacist invaded a Bible study session at the Emanuel African Methodist Episcopal Church in Charleston, S.C.
The recent spate of mass shootings led Tree of Life Rabbi Jeffrey Myers to write on the synagogue's blog, lamenting the lack of national action to address gun violence in the wake of the Parkland school shooting.
"Unless there is a dramatic turnaround in the midterm elections, I fear that the status quo will remain unchanged, and school shootings will resume," Myers wrote. "I shouldn't have to include in my daily morning prayers that God should watch over my wife and daughter, both teachers, and keep them safe. Where are our leaders?"
For months and years before the shooting, President Trump's critics have accused him up fueling bigotry, hatred and potential in his speeches - in which he, variously, encouraged violence against protesters and supporters; defended people who took part in a white nationalist rally in Charlottesville; and lately slammed "globalists" - a term that is commonly used as code for Jews in anti-Semitic circle, and which Bowers appears to have adopted in his online messages.
Trump has strongly condemned the synagogue attack. He ordered flags flown at half-mast at public grounds until sunset Wednesday in "solemn respect" for the victims. He has denounced the massacre in multiple speeches, including a political rally Saturday evening.
"This evil anti-Semitic attack is an assault on all of us," the president said. "It's an assault on humanity. It will require all of us working together to extract the hateful poison of anti-Semitism from our world."
As a solution, Trump proposed brining the death penalty "into vogue" and said the massacre could have been prevented if the synagogue had armed security guards - as he has suggested after other mass shootings.
At a news conference on Sunday morning, Pittsburgh Mayor Bill Peduto was asked about the president's response, and partially repudiated it.
"We will not try to rationalize irrational behavior," Peduto told reporters. "We will work to eradicate it. We will work to eradicate it from our city, and our nation, and our world. Hatred will not have a place anywhere."
