Rose of death (2007)

On prom night ten years ago, a group of drunken friends go too far when trying to scare a couple of their fellow classmates. After accidentally killing one of them, they decide they have to kill the other one in order to cover up the crime and protect themselves and their futures. Now, ten years later, as they start coming together for their high school reunion, each member of the group is being picked off one by one by a ghostly killer as some sort of revenge from beyond the grave.