You search the bathroom. It strikes you as odd that there aren't any partitions between the toilets but clearly there were supposed to be cubicle walls. Where have those partition walls gone, though?
You inspect further and realise that some of the marks on the walls aren't grime after all. They look like, well, scorch marks. Looks like hits from small arms fire.
You discover spent 9mm casings, an empty 9mm magazine for a handgun and chewed bubblegum.