The 11 people killed in the Pittsburgh synagogue shooting included a 97-year-old woman, the oldest victim, and a married couple.
Two brothers were also among those killed when a gunman opened fire during a baby naming ceremony at the Tree of Life Synagogue in the Squirrel Hill area on Saturday.
The suspect, who has been identified as 46-year-old Robert Bowers, faces 29 criminal counts.
At least six other people were wounded in the attack, including four police officers who rushed to the scene at after 911 calls from the synagogue just before 10am on Saturday, reported "they were being attacked".
The victims were named by the Allegheny County medical examiners' office as: Joyce Fienberg, 75, Richard Gottfried, 65, Jerry Rabinowitz, 66, Rose Mallinger, 97, Daniel Stein, 71, Melvin Wax, 88, David Rosenthal, 54, Cecil Rosenthal, 59, Irving Younger, 69, Bernice Simon, 84 and Sylvan Simon, 86.
It is understood the gunman had an assault rifle and several handguns when he opened fire on the synagogue containing up to 100 worshippers attending the ceremony.
City officials said the shooting was being investigated as a federal hate crime.
President Donald Trump condemned the “wicked act of mass murder” saying anti-Semitism “must be confronted anywhere and everywhere it appears”.
At a rally in Murphysboro, Illinois on Saturday evening, he issued a stark warning.
“Those seeking our destruction, we will seek their destruction. When you have crimes like this, whether it’s this one or another one on another group – we have to bring back the death penalty. They have to pay the ultimate price. They can’t do this. They can’t do this to our country – we must draw a line in the sand and say very strongly – never again.”
Earlier on Saturday when speaking to young farmers in Indianapolis, Trump called the attack “pure evil, hard to believe and frankly something that is unimaginable.”
After calling on the country to come together, Trump invited a pastor and rabbi on stage to pray.
Shortly after the incident Mr Trump spoke to reporters describing events as "far more devastating than anyone originally thought", adding that it's a 'terrible thing what's going on with hate in our country'.
The US president went on to say how the outcome would have been different with armed guards because the synagogue 'didn't have any protection'.
He also said shooters should receive the death penalty and "suffer the ultimate price."
Commander Jason Lando said the public should "shelter in place" and report any unusual activity.
Pennsylvania Gov. Tom Wolf called the shooting an "absolute tragedy."
He said: "We must all pray and hope for no more loss of life.
"But we have been saying "this one is too many" for far too long. Dangerous weapons are putting our citizens in harm's way."
The tree-lined residential neighborhood of Squirrel Hill, about 10 minutes from downtown Pittsburgh, has a heavily Jewish population.
Jeff Finkelstein of the Jewish Federation of Greater Pittsburgh told WPXI that the organisation's security officer has notified all JCC synagogues and they are on modified lockdown.