On the morning of August 20, 1986, Thomas Wade Shader Jr., 31, was at work in the Edmond Post Office when a part-time letter carrier opened fire. The shooter entered the facility armed with three handguns and killed fourteen people, including Shader, and wounded six others before dying by suicide at the scene.

Reports say the gunman had a history of erratic behavior and had been disciplined by supervisors; he was reportedly facing the possibility of being fired. No arrest was made because the suspect died during the attack. The massacre plunged Edmond into mourning and drew national attention to workplace violence and mental health.