Shannon grew up in the small town of Stillwater, Pennsylvania. She was born in 1955 (as seen on her gravestone when her husband/widower visits her grave on her birthday in Date With Destiny).
She properly met Leroy Jethro Gibbs while waiting for a train on the way out of town and the two quickly became good friends.
In 1980, Shannon became engaged to Gibbs. The pair married in December of 1981, having a daughter they named Kelly sometime in 1982.
In 1991, her husband was fighting in Desert Storm in Kuwait. At the same time, she witness a shooting of a Marine in Oceanside, and she identified the killer as Pedro Hernandez, a Mexican drug dealer working out of Camp Pendleton. Shannon agreed to testify against him. An NIS agent was assigned to protect her and Kelly, but Hernandez shot the agent in the head while he was driving. Special Agent Kurt Mitchell was killed instantly. Shannon and Kelly were both killed in the following car crash.
Shannon passed away at thirty-five years old.
NCIS Season 3
NCIS Season 5
NCIS Season 6
NCIS Season 7
NCIS Season 9
She is shown in flashbacks to be happily horseback riding with her husband and daughter on the beach, doing other family activities with them, and is the inspiration for Gibbs' list of rules, having created a set of her own prior to meeting Jethro.
Shannon was a woman of above average height, standing at 5ft7. She had red hair and blue eyes.