Thomas M. Dorn was a Marine Private First Class who served in the Marine Corps before dying after suffering a heart attack at the age of twenty-two. The history that Captain Brent Peters had taken revealed that Dorn was born on June 6th, 1978 and that he joined the United States in or around June 1999 before a car accident crushed his ankle, causing him to undergo surgery on May 15th, 2000 with Gunnery Vestman telling NCIS Special Agent Leroy Jethro Gibbs that he suspected Dorn had a coke addiction.