On April 19, 1995, a domestic terror attack led by Timothy McVeigh and Terry Nichols resulted in a truck bomb explosion on the Alfred P. Murrah Federal Building in Oklahoma City. The blast killed 168 people, including 19 children.

An Oklahoma City fireman walks near damaged cars on the north side of the Alfred P. Murrah Federal Building in Oklahoma City after a car bomb blast, April 19, 1995.
Jim Argo/The Daily Oklahoman/AP