Leeka was a Gunnery Sergeant assigned to the Naval Reserve Officers Training Corps and also a murderer who was responsible for the deaths of Sergeant Joseph Turner and Petty Officer Finnegan Blake.
In addition to that, he was also raping new recruit/fellowshipman Ashley Simmons by forcing her to sleep with him. When Turner and Blake confronted him after learning the truth from Simmons, intending to get him stop treating Simmons so badly, Leeka used his military training to kill both men by breaking their necks before dumping their bodies in two different places.
Turner's body was found first, prompting NCIS to be called in and mere hours or a day later, Special Agent Timothy McGee discovered Blake's body.
Gibbs later confronted Leeka over what had happened and the two got into a brutal fight which ended with Gibbs getting the upper hand while also beating Leeka into submission.
After recovering, Leeka was presumably arrested and jailed for both the killings and the rape of Midshipman Simmons while it's also likely that he was discharged for the Marine Corps for his crimes.
- Ashley Simmons (repeatedly raped.)
- Marine Sergeant Joseph Turner (neck snapped, killing him instantly with his body later being found by a drunk college student.)
- Petty Officer Finnegan Blake (neck snapped, buried in sand with Agents Timothy McGee, Leroy Jethro Gibbs, Anthony and DiNozzo finding the remains.)
- Leroy Jethro Gibbs (attempted, viciously assaulted, only for Gibbs to knock Leeka unconscious.)
- Was seen wearing a ring on his left index finger, suggesting that he might have been married.