" The defining difference between the spree killer and the mass murderer has to do with motion. Whereas the mass murderer slaughters in one place, the spree killer moves from site to site, killing as he goes. In that sense, spree killing might best be described as mobile mass murder. "

― Harold Schechter , The Serial Killer Files: The Who, What, Where, How, and Why of the World's Most Terrifying Murderers