Pittsburgh, PA - During the week, anyone who wanted to get inside Pittsburgh’s Tree of Life synagogue had to ring the doorbell and be granted entry by staff because the front door was kept locked. Not so on Saturday — the Jewish Sabbath — when the building was open for worship.

A gunman who had expressed hatred of Jews exploited that vulnerability, so common in so many houses of worship across the country, in a singularly horrific way.

Armed with a rifle and three handguns, the shooter walked inside the synagogue during Saturday morning worship and began firing, killing 11 and wounding six before police took him into custody, officials said. The attacker traded gunfire with police and was shot multiple times but survived.

The synagogue door was unlocked on the Sabbath “because people are coming for services, and the bell would be ringing constantly. So they do not lock the door, and anybody can just walk in,” said Marilyn Honigsberg, administrative assistant for New Light. “And that’s what this man did.”

Zachary Weiss, 26, said his father, 60-year-old Stephen Weiss, was inside the synagogue but was unharmed. Weiss said his father told him that he and Tree of Life’s rabbi helped congregants take shelter and follow the active-shooter response training they’d received months earlier. Stephen Weiss made it out of the building and used a janitor’s cellphone to call his family at home.

The attack, his son vowed, “will not define our congregation and will not define our city.”