Doom3 monster infighting *does* happen

[Job]

In the pumping station outside the area that leads to the Martian excavation site, you come under constant attack by chaingun guys and cacodemons. While I was getting rushed by a couple cacos and assaulted by a chaingun guy from afar, I put one of the cacos down with my shotgun while the other was a bit further back. It was hit by a stray bullet from the chaingun guy. I popped back out from a hall I was in, waiting for the caco - when I emerged from the hall, though, the caco closed the gap on the chaingun guy. Since the chaingun guy has no melee attack (that I know of anyway), he was pretty boned as the caco bit him to death.

[S1lent]

I've had monsters fight before. Mostly Archviles and commandos for me(delta labs). But I've seem zombies vs imps and Hell Knight vs Hell Knight.

[Deathmatcher]

I´ve also seen a Caco and a Chaingun Zombie (Demon?) fighting each other - well, actually only the Caco fought. It was the only time I noticed infighting.

[God Mode ON]

ive successfully created a mancubus vs fatzombie vs imp u gotta get the imp to use his fireball, and a chaingun zombie vs hellknight