[REC] (2007)
Found footage/mockumentary – a film maker and cameraman crew get locekd in with the inhabitants of a doomed apartment building. We have here a rather panicky, shouty protagonist with a sidekick who truly deserves the Nobel Peace Prize. The horror itself: classic base under siege material. People turn on each other as they try to make it out, so on and so forth.
Essentially this is Train to Busan in a building.