Frank McGuire was a Naval Commander who had top-security access to classified information. Not much is known about his family except for the fact that his parents are deceased and that he had a sister and a niece.
As such, due to his clearance, he became the target of an unnamed drug cartel who kidnapped him and forced to spend him three hours every morning, downloading information but McGuire sent emails to his laptop, emails that contained images of what he was being forced to steal, information that would come in handy for the NCIS: Office of Special Projects.
At some point during a gunfight, McGuire was executed by being shot in the head which was done presumably to stop him from talking to the police if he was captured. His body was later found by LAPD officers, prompting OSP to open an investigation into his death.