Blood on the Vault Floor

You all planned the heist for months, and it worked — until the fixer was found face-down beside the open vault, the take gone and one bullet missing from a gun that was supposed to stay unloaded. The building locks down in twenty minutes when the shift changes, and the cameras died at the exact moment he did. One of you doubled the count. One of you knew the combination nobody shared. Somebody moved the body before the rest arrived, and the story you agreed on already has a hole in it. Count the seconds, compare where each pair of hands was, and pin the killer among you — before the doors seal you all inside with the corpse.