PITTSBURGH — For more than two years the Tree of Life— Or L’Simcha synagogue, on a hilltop corner in the Squirrel Hill neighborhood of Pittsburgh, has sat heavy with memory but empty of worshipers.

Since the morning in October 2018 when a gunman showed up at Shabbat services and killed 11 worshipers, the somber building complex has been by turns a crime scene, a place of mourning and the subject of long, emotional discussions about its future. Slowly, over months of deliberation, the Tree of Life congregation came to decide that the building would be both its home for worship again as well as a commemorative site, a center for communal events and a place for people from all over the world to learn about confronting hatred.