From DoomWiki.org

A D-Man charging at the player.

D-men are enemies from Hacx. They are big, partly mutant and partly mechanical floating heads. Their only method of attack is to charge at the player. With 250 hit points, D-Men are very dangerous in big numbers as they are extremely fast and have a highly damaging attack. It is best to hit them with the uzi at a high distance as it should prevent them from attacking. Their lack of an awake sound also makes them difficult to locate at first.