Mass murder is the act of murdering a number of people, typically simultaneously or over a relatively short period of time and in close geographic proximity. The United States Congress defines mass killings as the killings of three or more people during an event with no "cooling-off period" between the homicides. A mass murder typically occurs in a single location where one or more people kill a couple others. A mass murder may be committed by individuals or organizations whereas a spree killing is committed by one or two individuals. Mass murderers differ from spree killers, who kill at two or more locations with almost no time break between murders and are not defined by the number of victims, and serial killers, who may kill people over long periods of time. The incidents of mass shootings are continuing to increase. By terrorist organizations Many terrorist groups in recent times have used the tactic of killing many victims to fulfill their political aims. Such incidents have included: 33 civilians killed in the Başbağlar attack by the PKK on July 5, 1993; 19 American airmen killed in the Khobar Towers bombing on June 25, 1996, by Hezbollah Al-Hejaz; 2,977 people killed by Al-Qaeda in the September 11 attacks of 2001; 193 people killed in the 2004 Madrid train bombings by Al-Qaeda; 334 (including 186 children) killed in the Beslan school siege on September 1–4, 2004 by Riyad-us Saliheen; 52 killed in the 2005 London bombings by Islamic terrorists; 166 killed in the 2008 Mumbai attacks by Lashkar-e-Taiba; 156 children and teachers killed in the 2014 Peshawar school massacre by Taliban in Peshawar, Pakistan; 130 killed as the result of the November 2015 Paris attacks by ISIS 1,095 killed in the Camp Speicher massacre by ISIS By cults Certain cults, especially religious cults, have committed a number of mass killings and mass murder–suicides. Jim Jones' Peoples Temple in Jonestown, Guyana, where 919 people died in 1978 Order of the Solar Temple in Canada, Switzerland, and France, where 75 died in 1994, 1995, and 1997 Shoko Asahara's Aum Shinrikyo, which killed 14 in Tokyo, Japan, in 1995 Marshall Applewhite's Heaven's Gate in San Diego, California, where 39 died in 1997 Movement for the Restoration of the Ten Commandments of God in Uganda, where 778 died in 2000 By individuals Mass murderers may be categorized into killers of family, of coworkers, of students, and of