MSCA refers primarily to natural disaster relief, but the term also includes a broad spectrum of other support operations. The Stafford Act contains four triggers for Federal disaster relief. The most widely used are the first two: the presidential declaration of a major disaster and an emergency. The other two triggers are: permitting the President to use the Department of Defense (DOD) resources in the immediate aftermath of an incident to preserve life and property; and allowing the President to declare an emergency when the affected area is one in which the United States (U.S.) exercises exclusive or preeminent responsibility and authority under the Constitution or U.S. law. The Immediate Response Authority exception to the Stafford Act authorized the use of medevac aircraft, ambulances, bomb detecting dog teams, and various military personnel in Oklahoma City. This exception permits a local commander, when time does not permit prior approval from higher headquarters, to provide assistance to local authorities in the case of emergencies. Commanders at nearby military bases relied on the Immediate Response Authority to provide help within minutes of the blast, and those same commanders, along with units all over the country, supplied additional disaster relief support over the course of the next week under the authority of the Stafford Act. The Murrah Federal Building was a Federal crime scene, requiring the exercise of legal authorities which permitted, and also limited, the support the DOD could send to aid civilian law enforcement agencies that were providing security and investigating the crime. 34 notes.