mass casualty incident ( often shortened to MCI and sometimes called a multiple-casualty incident or multiple-casualty situation ) is any incident in which emergency medical services resources , such as personnel and equipment , are overwhelmed by the number and severity of casualties . For example , an incident where a two-person crew is responding to a motor vehicle collision with three severely injured people could be considered a mass casualty incident . The general public more commonly recognizes events such as building collapses , train and bus collisions , plane crashes , earthquakes and other large-scale emergencies as mass casualty incidents . Events such as the Oklahoma City bombing in 1995 and the September 11 attacks in 2001 are well-publicized examples of mass casualty incidents . The most common types of MCIs are generally caused by terrorism , mass-transportation accidents , or natural disasters
Oklahoma City bombing
Oklahoma City bombing
Mass-casualty incident