The One Thing Gibbs Couldn't Keep A Secret About On NCIS

Leroy Jethro Gibbs, played by Mark Harmon, is a fan-favorite NCIS character for a reason. He's got the buttoned-down professionalism of a young Agent K from Men in Black, mixed with, well, the age of a contemporary Agent K from Men in Black. Perhaps most important to Gibbs' oeuvre of personality traits, however, is his devotion to almost monk-like silence. He keeps himself to himself, doesn't dole out compliments, and generally gives off the vibe of a new girlfriend's dad whom you've just met for the first time and who hasn't blinked in 20 minutes. For entire seasons, NCIS has dangled questions about Gibbs' life in front of audiences like tantalizing, steely-eyed carrots on strings. How does he get his boats out of the basement? Why did he shoot McGee? Most importantly — no, really — how does Gibbes get his boats out of the basement?

That said, there's one secret that Gibbs couldn't keep from his colleagues, and it's a doozy. Back in the season 16 episode "...and Executioner," the familial crew at the Naval Criminal Investigative Service learn that Jethro Gibbs isn't just the father figure whose approval they would spend the rest of their lives pursuing in a Sisyphean frenzy of daddy issues. He's also a cold-blooded murderer.

Before this reveal, longtime viewers were already aware that Gibbs had been married on a handful of occasions, and that his first wife, Shannon, was killed in the early '90s. She was set to testify against a ruthless drug dealer, Pedro Hernandez, and a federal agent was escorting her and the couple's daughter, Kelly. On the car ride, Hernandez shot the agent driving the car, killing Gibbs' dearly beloved and bright-eyed kid.

As a result of this heinous crime, Gibbs went on a Wyatt Earp revenge ride, taking the law into his own hands by tracking down and killing Hernandez. He even left enough evidence behind to link him to the vigilante killing, but the investigation was closed without charges being brought against him (in a shady government case of teamwork making the dream work).

Gibbs has always been portrayed as the kind of guy who looks in the mirror and reminds himself what snitches get, following the credo that "the best way to keep a secret is to keep it to yourself." But in NCIS season 16, he opened up to his colleagues, admitting to going full Punisher on a trip to Mexico. While he hasn't yet faced consequences for his actions, this tantalizing development opens up the world of NCIS to plenty more stories down the road.