A mass killing, as defined by a genocide scholar Ervin Staub, is "killing members of a group without the intention to eliminate the whole group or killing large numbers of people without a precise definition of group membership".[1][nb 1] This term is used by a number of genocide scholars because the term "genocide" (its strict definition) does not cover mass killing events when no specific ethnic or religious group is targeted, and when perpetrators are not intended to eliminate of the whole group or its significant part. This article primarily discusses different models used by genocide scholars to explain and predict the onset of mass killing events.