Spree murders that cross into the category of mass murder are those that involve movement in tight locations (MTL) and a brief time period, from a few minutes to no more than a few hours. In this category, the offender’s movement is nearly always on foot. Selecting victims requires the killer to move from one distinct and often isolated location to another. It’s not as simple as going room to room in a residence, and no sprees with these criteria are included in this category. The movement for this type of spree requires the killer to make a deliberate effort to locate targets.