The POC or Primary Operations Complex is a large building filled with dozens of people, some who are guards. Most if not all of these guards were killed during the events of Aliens versus Predator 2, most of this is done off-screen with the information only being known by finding emails, notes and some reports filed by Joss Blaney who became concerned about the number of missing guards.
Joss Blaney: He seems to have been the leader of a group of guards and convicts who were forced together while trapped among the Xenomorph infestation. On November 28, 2230, Blaney reports the POC Commander dead, although he presumably died quite some time before that. He still expects General Rykov to come to the POC survivors' aid. On December 10, he reveals that most sentry guns are dead due to failing power generators. He maintains strict discipline, putting anyone who misses a rotation on half-rations and closing the hideout's gate at sundown - regardless of whether anyone's still inside.
On December 15, he reports guards Brown, Miller and Thabideau missing, probably dead. On December 26, guards Cheever, Kaplan, Pendleton and Murray are dead.
Cisco: he is typified as an unfriendly, confrontational character, constantly berating others for not doing their job correctly (in his opinion). He is said to have "issues" and doesn't have any friends. Judging from the submissive manner in which several other guards respond to him after being berated from not being on their usual post, as well as his dismissing of a sergeant's orders (albeit without said sergeant present), it can be surmised that he has a position of authority. He is later killed by a Chestburster after being impregnated by a Facehugger.
Brown: Missing. Miller: Missing. Thabideau: Missing. Cheever: Deceased. Kaplan: Deceased Pendleton: Deceased. Murray: Deceased.
Most if not all guards would have very likely been killed not just by the infestation but by Tomiko self-destructing the base.