vkrp6w He was serving in Operation Desert Storm as a sniper when a drug cartel member named Pedro Juan Hernandez (Thomas Rosales Jr.) killed Shannon, who was going to testify against him. Upon discovering this, Gibbs went in search of their killer and sought vengeance during the episode “Hiatus, Part 1.”
While viewers know of the incident, it’s mostly been hidden from people Gibbs works with, although characters who know Gibbs’ history have told others here and there. After all the comings and goings of cast members over the years, a handful remain keepers of the secret that would probably land Gibbs in some legal hot water, if the wrong people found out.
In an episode that aired during Season 16, “…And Executioner,” that happened. A shadowy network of vigilantes, first discovered in the previous episode, “Judge, Jury…,” sentences Gibbs to death for his long-ago crime, targeting him through hitwoman Mallory (Dionne Gipson). Gibbs confronts Judge Deakin (Mike Farrell) but also tells his team about his transgression.