My first thought is Fear Dot Com.
Any more detail you can provide on this? Do you recall when you last watched the film?
Thanks to your reply.
It's not Fear Dot Com, maybe more similar to a campus movie.
Sorry to I have only some broken memories about this movie, there are some clips in my mind:
1. The girl seems to put the gun up in the school.
2. The mobile phone in this movie could play video, maybe a folder type, I watched this movie between 2000~2011, or not so early.
3. "Maybe" there is a scene but I am not sure it's in the same movie, some classmate messed their home while they have the party, the step-brother was upset for it. Also they drugs in the party.