Dr. Michaels

Dr. Michaels was a UAC scientist who worked in Delta Labs. He was one of the few people who survived the first wave of the demonic invasion. During the invasion, Dr. Michaels locked himself in his research lab and began studying the corpse of an Imp brought back earlier from one of the Portal expeditions, hoping to find a weakness.

The Player encounters Dr. Michaels in his lab. Michaels gives the Player the code (624) for a pair of supply cabinets in the adjacent room, then asks him to go get help. What happens to Michaels is unknown, but there's a good chance he was killed offscreen since the Resurrection of Evil intro states that the Marine was the only survivor.

The Bio-Suit Zombie model in Resurrection of Evil is a modification of his model, which is also shared by the anonymous individual who is killed by the Hell knights in the Delta Labs.