Former human monsters, as a conceptual family of enemy types, are humans that have been slain and reanimated, or "zombified", by the evil forces of Hell, and taken as a group they are Doom's most common enemies, especially in early levels.
They were once soldiers, like the player's marine, or UAC security guards, but have been somehow turned undead and now serve the demons they once fought. Inside the Doom source code and in the Doom Bible they are called Possessed humans, and their sprite prefix always contains an abbreviation for "possessed". Because of their immediately human origin, they attack with hand-held firearms instead of innate abilities or cybernetic implants as other monsters do, and their low speed and durability makes them easier to eliminate than most of their fully demonic counterparts. Because of their very low hit points, they are often gibbed when struck by more powerful opponents.
Powers and Stats
Tier: Varies from 9-C to 9-B
Name: Former Human, Z-Sec, Rifleman/Shotgun Guy (Doom 1 and 2 only)
Gender: Only male soldiers were shown
Age: Varies (from 20's to 40's)
Classification: Possessed humans
Attack Potency: Varies from Street level to Wall level depending on the variant. (The caliber of the guns they carry easily bypasses 1,000 joules of energy. The pistol is a Desert Eagle, which has an energy output of around 2,000 joules. The Zombieman carries an M4, which has an energy output of 1,570 joules. A few of the Z-Sec Soldiers carry machineguns based on the P90, the shotgunner carries a 12-gauge, and a number of Commandos carry chainguns.)
Lifting Strength: Unknown, likely Peak Human
Durability: Street level (Most are either killed or severely wounded with a single shotgun blast, but are capable of surviving several shots from a Desert Eagle or a machinegun.)
Stamina: Seemingly unlimited (They won't stop unless the demon's soul leaves their body.)
Range: Standard melee range physically. A few meters with shotguns. Likely a few dozen meters at most with firearms. (Their aiming proficiency seems to deteriorate at longer distances.)
Standard Equipment: Ranges from blunt weapons and pistols to shotguns, machineguns, rifles, riot shields and chainguns.
Intelligence: Average at best. Despite being shown flanking their opponents in fairly intelligent ways, they are only capable of attacking and are fairly unintelligent in regards to battle tactics. They are also often prone to attacking anything that damages them, even those who are supposed to be on their side.
Weaknesses: Cannon fodder with limited intelligence and extremely low movement speed compared to other enemies in the series. Their only real strength lies in their numbers.