Retired Investigator had a 27 year career in law enforcement. Three years were as a "street cop" (Deputy Sheriff) and 24 years as an FBI Special Agent. Prior to law enforcement, Retired Investigator served in the US Army during the tail-end of the Vietnam war. He was a paratrooper in the 82nd Airborne Division, serving in the Airborne Infantry, attaining the NCO rank of E-5. After college, he entered the US Air Force, Officer Training School (OTS) and received an Officer's commission. He received additional training in the USAF Security Police (now Security Forces) career field. During the 1980's, he received an appointment to the FBI as a Special Agent. He spent approximately half his career investigating criminal matters and the other half involved in National Security. During 2017, his "DB Cooper" theory was portrayed in an episode of EXPEDITION UNKNOWN, hosted by Josh Gates on television's TRAVEL CHANNEL. Retired Investigator participated in the film production during location shooting in Seattle, Washington and Reno, Nevada. Additionally, he has appeared as a WWII military historian on the History Channel. For that documentary, he traveled with the film crew to the Philippines for location shooting. He has a WWII historical novel based on the same event. The novel's website is: www.notforgottennovel.com . For additional background information, view author's LINKEDIN profile at "Gregory Hall of greater Las Vegas"