A school shooting is a form of mass shooting involving a gun attack on an educational institution, such as a school or university. The U.S. Secret Service defines them as shootings where schools are "deliberately selected as the location for the attack". These shootings have sparked a political debate over gun violence, zero tolerance policies and gun control. While educational institutions are subject to attacks by outside terrorist groups (for example the Garissa University College attack), this article mainly covers students who plan and carry out murders on their campuses.