ACOP Shawn Mayo began his career with the Billings Police Department in 2001. He worked night and noon shifts as a patrol officer until his promotions to sergeant in 2007. During his time as a sergeant, he continued to work in the Patrol Division until he transferred to the Detective Division in 2013. Mayo worked as a detective sergeant until his promotion to lieutenant in 2015. Since then, he had served in the patrol division as a shift lieutenant. In 2022, Captain Mayo retired from SWAT as the SWAT commander after nearly 18 years on the team. After serving a brief stint as the Captain of Investigation, Mayo was promoted to the Assistant Chief of Police in February of 2025.