I can't remember the name of this gory slasher movie.?

I watched this slasher movie ast year and i'm not sure what year it was made i'm pretty sure it was 2007 or 2008. all i remember is this group of friends are out in the middle of nowhere either on a trip or car broke down i cant remember. also i remember this really gross part where this guy is hiding in a bathroom and its really really gross and the killer walks in with plyers and crushes the guys testicles. last thing i remember is the friends are snooping around and find tapes of people being killed. i really hope somebody can tell me what its called