A mass shooting is a violent crime in which one or more attackers kill or injure multiple individuals simultaneously using a firearm. There is no widely accepted definition of "mass shooting" and different organizations tracking such incidents use different definitions. Definitions of mass shootings exclude warfare and sometimes exclude instances of gang violence, armed robberies, familicides and terrorism. The perpetrator of an ongoing mass shooting may be referred to as an active shooter.

On the morning of 18 November 2014, two Palestinian men from Jerusalem entered Kehilat Bnei Torah synagogue, in the Har Nof neighborhood of Jerusalem, and attacked the praying congregants with axes, knives, and a gun. They killed four dual-nationality worshippers, and critically wounded a responding Druze Israeli police officer, who later died of his wounds. They also injured seven male worshippers, one of whom never woke up from a coma and died 11 months later. The two attackers were then shot dead by the police.