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 (poorly) barricaded 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 and possibly to keep his sanity at bay.

The Player encounters Dr. Michaels in his lab. He is frightened at first but is relieved that the player is not a demon. Michaels gives the Player the code (624) for a pair of supply cabinets in the adjacent room, then asks him to go get help and states he does not want to leave his lab. 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.