HEV suit guys on xen



I was recently playing HL again and came across something i didn't remember. Forgive me if my question is dumb and I'm just not thinking. All over xen (in different areas) there are dead bodies. These people are all wearing HEV suits. They usually have some helpful gear around them like batteries for the HEV suit, medpacks, ammo, or whatever. Who are these guys supposed to be exactly?
Yeah, I think they were just the guys heading there to pick up the crystals.
I found her in Opposing Force by chance, using the teleporter gun to escape certain death from a Black Ops gunship. She looks like the HEV suit coach in Half Life's Hazard Course, anyone else got any ideas who it might be? Unless they just added her in for "decoration"..
It's Gina Cross, she's one of the characters from Decay. Which is weird, because Gina doesn't die (You know, die die) in Decay...

So, what do we believe? Decay or Opposing Force?
Was Decay the release for the Dreamcast / Playstation? I've never played it, what happens in that version? :)