O n October 27, 2018, a man armed with an AR-15 rifle and multiple handguns entered the Tree of Life synagogue in Pittsburgh, Pennsylvania. Spouting anti-Semitic slurs, after posting numerous anti-Semitic sentiments online as well, he entered the synagogue and began randomly shooting. He killed 11 people, predominantly older adults doing nothing more than participating in religious services, and injured many others. While attempting to leave he was confronted by law enforcement officers, and he then fled back inside and barricaded himself for a short time before surrendering to police.The attack on the Tree of Life Synagogue was the deadliest attack on Jews in U.S. history, leaving the Squirrel Hill and Pittsburgh area devastated and the Jewish community rocked. Bias-based violence has been a consistent part of the human experience, but only since the late 20th century have bias crimes been recognized as a unique type of crime in many legal and social systems with unique impacts. Although bias crimes (also known as hate crimes) are defined differently across jurisdictions, the definition typically involves two parts-a base offense (e.g., an assault, vandalism) and a determination that the base offense occurred in whole or in part as a result of the perpetrator's bias against a group or identity (e.g., race, ethnicity, religion). Bias crimes have also been called message crimes because they send a message that someone is "different," unwanted, and less valuable than others in the community (e.g.