At 59:30, Alex picks up a gun from the floor. He fires several shots, and then is out of ammunition - click, click, click. The slide on the automatic pistol should have locked in the rear position as all autoloaders do after the last round is fired, but it didn't lock back.
At approximately 27:00, Anna goes to the front door. The chain lock is looped and stowed up On the right side door. When Alex secures the doors at 27:58, the chain lock is dangling down the full length of the chain.