The Mutilator

On the day of his father's birthday, the boy Ed decides to clean his father's hunting rifle and accidentally shoots and kills his mother that was baking a cake in the kitchen. His father Ed Sr. is mentally affected by the incident. Years later, Ed is in a bar with college friends and they do not know what to do in the holidays, since they have not reserved any place to go. Out of the blue, Ed receives a phone call from his estranged father that asks him to close his fishing house in an island since it is off season. His friends invite themselves to go with him and spend a couple of days on the beach. Ed drives to the island with his girlfriend Pam and the couples Ralph and Sue, and Mike and Linda. They find the house open and an ax missing, but do not report to the police. Further, there is anyone in the island but them. Soon a killer starts to kill them one by one and hang them in a locker in the house garage. Who might be the serial-killer?