Captain Gaa began his law enforcement career with the Peoria County Sheriffs Office in 1993 in the Patrol Division.
He was part of the implementation of the Community Policing Program, serving as a Community Police Officer for the City of West Peoria. As a Deputy with the Peoria County Sheriff's Office, in addition to his patrol assignments, he fulfilled additional roles as a Master Firearms Instructor and a Tactical Team Operator. He received the Deputy of the Year Award in 1998. He was promoted to Lieutenant in 2002 being assigned to the Patrol Division. In 2009 he was assigned the Tactical Commander of the Central Illinois Emergency Response Team and the Tactical Commander of the Illinois Law Enforcement Alarm System (ILEAS) Weapon of Mass Destruction Special Response Team.
Captain Gaa is a graduate of Illinois Central College and Northwestern School of Staff and Command. In his current assignment, Captain Gaa is the supervisor over the Peoria County Courthouse Court Security and Civil Process Division.