What to Know as the Tree of Life Massacre Trial Begins

Members of all three congregations were killed in the attack. The victims were Joyce Fienberg, 75; Richard Gottfried, 65; Rose Mallinger, 97; Daniel Stein, 71; Melvin Wax, 87; Irving Younger, 69; Jerry Rabinowitz, 66; the couple Bernice, 84, and Sylvan Simon, 87; and the brothers Cecil, 59, and David Rosenthal, 54.

Six people were wounded, including four police officers.

The attack drew shock and outrage from across the world, and brought people from across religious communities in Pittsburgh together in support of the congregations that were attacked. Some members of Dor Hadash created a nonprofit to lobby for new gun laws. The Tree of Life building, which sat empty for years after the massacre, is being redesigned by the architect Daniel Libeskind and will soon become the home of a new organization dedicated to ending antisemitism. On Sunday, members of the Tree of Life congregation gathered in the synagogue garden to say goodbye to their old building.

Who is the accused gunman?

Mr. Bowers grew up in a Pittsburgh suburb, raised by his mother and extended family. When he was a child, his estranged father was charged with raping a woman in the same neighborhood where the mass shooting would later happen, and killed himself before trial.

After high school, Mr. Bowers worked as a delivery driver for a bakery and later as a long-haul trucker. He tinkered with electronics, worked on the website of a conservative talk radio show, and, neighbors said, kept mostly to himself, at least in the offline world.

Online, he was a prolific and virulent presence on right-wing forums, chatting with and reposting prominent white supremacists and in his own posts showing particular vitriol toward immigrants and Jews.