I was just doing that mission the other night, and I stopped to look. It's a perfectly clean research center, except for those dead bodies by the entrance. Watching Pompeii documentaries on Netflix has given me the expertise to discern that bodies laying near an entrance means they're trying to escape. They locked themselves in during the Collapse, and couldn't get out when they needed to. The Fallen have apparently found more than one way to get in, so they could also have been survivors that locked themselves in, but fled to that last exit when the Fallen later broke in elsewhere. Their clothes are also missing, but they could be dust by now.