What is the name of this movie?? *contains spoilers*?

I cant remember the name of this movie. Here is what I remember from it. If you know the movie, could you tell me the name?

A couple stay at this lake for their anniversary or something like that. They get harrassed by this group of teenagers with a dog. Their car winds up getting stolen by the teenagers, so the husband goes to retreive it. A fight or something takes place and the group's dog ends up killed. The distrought owner of the dog surrenders the keys to they car and tells the couple to leave. The group then stalks and terrorises the couple. Eventually, the husband gets captured and tortured by the group while they record it with a cell phone. A bunch of other stuff that I cannot recall happens. The husband sends his wife out to find a clinic because he is bleeding to death. During her search, she runs into this kid they apparently met earlier in the movie, probably before I started watching it. The kids said he was waiting for his mom to pick him up, and he starts playing with his cell phone. When asked if he gets a signal, he claims he is just playing a game. Not too long after that, the group of teens shows up. It turns out the forced to boy to find her and tell them when he did, that is what he was really doing on his phone. The wife finds herself tied up by her husband, who had already bled to death waiting, and was dead. The teens set his corpse on fire, and asked him if he was warm. The wife manages to escape, and the group kills the boy by setting him on fire. The wife then arms herself with some broken glass, and kills some of the teens. She eventually finds herself at a house where some sort of party is going on. Some stuff is said, and it turns out that the people at the party are the parents of the group of teens. The parents discover that some of their kids were dead. And one of the kids returns home. He is hit by his father, and he goes upstairs. The wife is dragged into a bathroom and killed. The kid is shown deleting the torture video.