It was made between 2000 and 2007, coloured american film.

The film was about this teenager/young adult who had been turned into a snake-like creature and he was killing people he knew who had bullied him. One scene I remember is the group were trying to escape in there car through the woods and a girl was leaning out a window and either got grabbed by the monster or caught on a tree branch. Another scene later on was the main girl in a pit of dead bodies with a guy who sacrificed himself so she wouldn’t be killed when the creature came back but I think the creature recalled liking her when he was still human so he let her live in the end.