Jason King is a detective in the Baltimore Police Department.
When he was nine years old, the townhouse Jason was staying in caught on fire due to an arson attack. He ended up saved by then-civilian Anthony DiNozzo, although he held a grudge against DiNozzo since he was unable to save his four year old sister from the fire, due to burning wreckage preventing him from getting to her and thus greatly increasing the risk of all three of them dying in the fire. Because of this incident, he later joined the Baltimore Police Department to investigate homicides, and later arson-related crimes by February of 2012.
Two months after his promotion, his and DiNozzo's paths would eventually be crossed again, when an arson-related fire in a warehouse resulted in the death of an apparent member of an Equinox's development team, as well as the theft of classified files of the United States Navy, requiring the involvement of both the BPD and the NCIS. They investigated the nature of the victim's death, and also went to a docked cargo vessel after an arson was reported on its deck. However, what they stumbled upon was a death trap relating to faulty wiring (later discovered to be developed by Equinox) and thermite, a death trap that he and DiNozzo only narrowly evaded by sealing the airlock door that would have detonated the entire ship.
He along with NCIS Forensic Scientist Abigail Sciuto later identified the missing ingredient of thermite to avoid burning a hole (a common problem with thermite), although they weren't able to arrest the person responsible, Bruce Johnson, or learn the identity of the person who hired him for the arson due to his car being rigged with the explosive, and DiNozzo also stopped him from attempting to save him as he realized it was far too late for him, much to King's consternation, although they did manage to retrieve the file stolen and learned that only a third of the vessels updated the wiring to not include the faulty system. He and DiNozzo later made peace when DiNozzo explained that it was because of the fire that he became a BPD police officer and later an NCIS agent and left in good terms.