Colin Sullivan joined the NYPD in 2011 and began his career on patrol in the Midtown South Precinct In 2013, Sullivan was assigned to the 6th Precinct in Manhattan's Greenwich Village, ultimately serving as the Assistant Field Intelligence Officer for the 6th Precinct. In 2018, Sullivan was assigned to the Intelligence Division International/Domestic Liaison Unit Operation Sentry Program. Sentry is a nationwide domestic network of trusted law enforcement partners amongst more than 400 law enforcement agencies throughout the United States. In 2020, Sullivan was promoted to Detective, and in 2021, he was selected to the 28th class of the NYPD Hostage Negotiation Team. He was promoted to the rank of Sergeant 2022. Sullivan was assigned to the 1st Precinct in Lower Manhattan and was designated as the Field Intelligence Sergeant for the 1st Precinct. In 2024, Sullivan was transferred to the NYPD's Hostage Negotiation Team. He currently serves as the team's Assistant Coordinator, responsible for supervising HNT requests for service, assisting in the recruitment of new negotiators and the training of active team members, and organizing the team's annual negotiator conference.