The W column gives a basic description of the weapons used: This is a list of mass/spree killers who attacked schools.
A mass murderer is typically defined as someone who kills three or more people in one incident, with no "cooling off" period.
[76][77] A mass murder typically occurs in a single location where one or more persons kill several others.
[78][79][80] The victims must be largely the relatives of the perpetrator to be considered a familicide.
This list does not include serial killers, members of democidal governments, or major political figures who orchestrated such actions.