He was one of the people wounded during the assassination attempt on US President Ronald Reagan on Monday, March 30, 1981, in Washington, D.C. From Pittsburgh, Pennsylvania, Thomas Delahanty joined the Metropolitan Police Department of the District of Columbia in September 1963 after working for Jones and Laughlin Steel (1959–1963) and serving in the United States Navy (1955–1959).

[1] Reagan, White House Press Secretary James Brady, and United States Secret Service agent Timothy McCarthy were also wounded in the crossfire.

On April 2, after learning that the others could explode at any time, volunteer doctors wearing bulletproof vests removed the bullet from Delahanty's neck.

His argument against the manufacturer—that small, cheap guns have no purpose except for crime, and thus the company should be held responsible—was rejected by the District of Columbia Court of Appeals.

[10] Delahanty lives in Whitehall Borough, Pennsylvania[11] (a suburb of Pittsburgh), after having moved from suburban Washington, D.C., after the death of his wife, Jean Marcey (1926–1997).