Years ago, I watched a movie about two girls, students (if I’m not mistaken). They were going somewhere (probably for a holiday) on a bus with other passengers. Then, their bus got crushed by something, and they were around an abandoned hotel (unsure if it was a hotel or something else). They ran to the hotel as some killer was following them all and killed everyone. The girls were recording all the things. In the end, it turns out that the two girls were the ones who were killing everyone there. They were changing the costume of “killer” and going and killing everyone just to shoot a movie.