Detour or Dead End type movie on Syfy?

There was a movie I watched on Syfy a while back.I remember one of the scenes a girl was trapped at a gas station with a murder after her.The police officer that tried to help her was attacked by the murder and was dying inside the gas station. (not to get gruesome here) But I also recall the murderer trying to bite her finger off when she was trying to escape. If anyone knows the movie title,please let me know.