A government helicopter pilot reported a near miss with a UAS in controlled airspace. The helicopter pilot took evasive action to avoid a possible collision.

Narrative

On Day 0 at around XA25 hours I was flying my law enforcement helicopter; Airbus AS350; Aircraft X; for the local law enforcement over the city. While orbiting over a law enforcement call at 900 feet MLS; I saw a UAS/Drone; within about 100 feet of my aircraft at the same altitude then it climbed between 1000 feet and 1100 feet. This occurred within ZZZ surface Class C airspace approximately; 2 miles northwest of the airfield. The nearest cross streets on the ground were; Street X and Street Y. I had to do evasive maneuvers to avoid a collision with the drone. The drone appeared to be a possible quadcopter and had flashing red and green lights. I avoided the drone and flew away from it to the north while we continued to work our law enforcement mission. We were unable to locate the source/operator of the drone because of the priority for our law enforcement call that were were assigned. Our law enforcement call was watching an event move in the city and this drone may have been related to that incident.