Running after the civilian, you couldn't help but notice the stench of rotting flesh got increasingly stronger. It didn't take long to catch up to Bob, though - all you had to do was home in on the sounds of someone being violently ill.
You found Bob standing next to a door and half-way through losing his lunch. He had a good reason to, though... The corridor opened into a big public atrium, but the open space was presently littered with civilian corpses in various stages of dismemberment. Men, women, children... plenty of blood and unidentifiable pieces of flesh strewn around as well. You could see doors to living quarters lining the walls. Only a handful were closed. The smell of death was almost overwhelming.
The atrium itself was like a ring plaza surrounding the tower's central support pillar, plenty of benches, a few potted trees, big, open spaces and the like. The floor seemed to terminate a short way off from the pillar's walls, but there looked to be a glass wall or other similar barrier in the way to keep people from falling in... judging by some of the bloodstains. Spiral staircases could be seen in six spots around the plaza, going both up and down, and wider ramps were visible by the outer walls of the chamber.
There weren't any aliens here that you could see, just a lot of dead bodies.
