Sgt. Neil Carlsen was an officer of the Raccoon City Police Department On the 20th, he filed the Patrol Report, where he reported seeing a suspicious man hanging around in the sewers. He also discovered military-grade weapons presumably dropped by the man, which were placed in the RPD's confiscation room and later used by Claire Redfield.
He was later killed in the RPD library by the insane Chief of Police, Brian Irons. One of several who suffered this fate when Irons' took to hunting his former colleagues like game.