The victims' names were released Sunday morning by the Allegheny County medical examiner's office, one day after authorities say Robert Bowers opened fire during a weekly service at the Tree of Life synagogue in Pittsburgh.
Scott Brady, the U.S. attorney for Pittsburgh, said federal prosecutors were seeking approval from the Justice Department to pursue the death penalty, The Associated Press reported Sunday night.
Cecil Rosenthal, 59, and David Rosenthal, 54, both of Squirrel Hill, were brothers, said Dr. Karl Williams, the chief medical examiner. Sylvan Simon, 86, and his wife, Bernice Simon, 84, both of Wilkinsburg, were killed Saturday morning at same synagogue where they had wed in a candlelight ceremony in December 1956, according to Pittsburgh's Tribune-Review newspaper.
The youngest victim was David Rosenthal. The oldest was Rose Mallinger, 97.
The other victims were:
Joyce Fienberg, 75, of Oakland, city of Pittsburgh
Richard Gottfried, 65, of Ross Township
Jerry Rabinowitz, 66, of Edgewood Borough
Daniel Stein, 71, of Squirrel Hill
Melvin Wax, 86, of Squirrel Hill
Irving Younger, 69, of Mount Washington
Williams said at a news conference that the victims' families has all been notified and were "are in shock" and "grieving."
Friends and loved ones remembered those who were killed as kind, devoted to spiritual life at the synagogue and loving toward one another.
Michael Stepaniak, who knew the Simons for decades, told the Tribune-Review that the pair were "a loving couple, and they've been together forever. I hope they didn't suffer much, and I miss them terribly."
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Myron Snider, a friend of Wax, a retired accountant, described his friend to The Associated Press as "such a kind, kind person."
He said Wax was a pillar of the congregation, according to the AP.
"He went Friday night, Saturday and Sunday, when there were Sunday services," Snider said. "If somebody didn't come that was supposed to lead services, he could lead the services and do everything. He knew how to do everything at the synagogue. He was really a very learned person."
Stephen Cohen, co-president of New Light Congregation, told the AP that "the loss is incalculable."
Stein and Gottfried made up "the religious heart" of the congregation and would help the rabbi with everything that needed to be done to hold services, Cohen said.
Zachary Weiss, whose father was filling in for the rabbi at the Tree of Life congregation, told NBC News on Saturday that his father told him that when the shooting began, it initially sounded like a "car crash."
But soon it became clear that they were dealing with an active shooter, Weiss said.
"My father was able to make sure that everybody was hidden, whether it's in the back or they were hidden in place," he said, adding that his father went downstairs to check on another congregation.
At one point, his father saw shell casings moving, but he didn't get a clear look at the gunman, Weiss said.
Weiss said he hoped people would remember the victims, as well the first responders. He called for the city to come together amid the tragedy.
"I'm literally seething, and my heart breaks for so many people," Weiss said.
Carnegie Mellon University said Fienberg was the widow of a longtime university and "herself a valued member of our community for almost 40 years." It said it was scheduling a program for Monday afternoon to remember her and the other victims.
Daniella Silva is a reporter for NBC News, specializing in immigration and inclusion issues, as well as coverage of Latin America.