For example, in the fourth episode of season six, Heartland, the team discover Gibb’s first wife, Shannon Fielding (Aviva Baumann), and his daughter was murdered by a drug dealer.
Viewers also discovered Gibbs was an integral member of the US Marine Corps and became a Scout Sniper.
He took part in Operation Just Cause in Panama and Operation Desert Storm in the Persian Gulf before retiring after a classified mission in Colombia.
Although he is introduced as part of the reserves in parent series JAG, Gibbs is retconned to have retired with the rank of Gunnery Sergeant.
