Friday the 13th Part 3: 3D

Following the events of the previous film, Jason, seriously injured after his encounter, goes to a lakefront store to find clothes. While there he kills owner Harold by slamming a meat cleaver into his chest, and stabs Harold's wife Edna in the back of the head with a knitting needle. At the same time, Chris Higgins and her friends return to Higgins' Haven to spend the weekend. The gang includes pregnant Debbie, her boyfriend Andy, prankster Shelley, his blind date Vera (who does not reciprocate his feelings), stoners Chuck and Chili, and Chris' boyfriend Rick.
Shelley and Vera inadvertently run afoul of bikers Ali, Loco and Fox at a convenience store. After being wronged, Shelley stands up for himself by running over their motorcycles, impressing Vera. Rick loses his temper after seeing the window of his Volkswagen Beetle smashed in and leaves with Chris. Meanwhile, Jason has hidden in the barn to recover from his injuries, and when the bikers show up to siphon their gas with the intention of burning down the barn to get even, he kills Loco and Fox with pitchforks and seemingly kills Ali with a pipe wrench. As night falls, Jason slashes Shelley's throat and dons the hockey mask to conceal his face. After shooting Vera through the eye with a speargun, he moves into the house where he kills Andy by slicing him in half as he walks on his hands. He shoves a knife through Debbie's neck while she is resting on a hammock. When the power goes out in the house, Chili sends Chuck down to the basement to check on the power. Jason throws Chuck into the fuse box and kills him, severing power to the house. Jason kills Chili by impaling her with a red hot fireplace poker.
Chris tells Rick about a time she was attacked by a horrible, disfigured man two years earlier, which was the reason she moved away. Rick's car dies and they have to walk back to the Haven, which they find in disarray. Rick steps outside to search the grounds, but Jason grabs him just beside the cabin. As Chris calls out to him from the front door, Jason holds him back just out of sight and keeps one hand held over his mouth. While Chris goes back inside, Jason kills Rick by crushing his skull with his bare hands until one of his eyeballs pops out. Chris discovers bloody clothes in the overflowing tub upstairs. She runs outside and is surprised by Loco's corpse dropping down from a rope on a tree limb. Chris runs back inside, and Jason throws Rick's corpse through the window.
Terrorized and panicked, she dumps a bookcase on Jason and hides upstairs in a hall closet. She discovers Debbie's body, and narrowly escapes the house and tries to escape in her van, which breaks down after having been siphoned by Ali and the others. She makes her way to the barn where she tries to hide and is attacked again by Jason. She lures Jason up to the loft and sends him through the window, hanging him, but he breaks free, much to Chris' horror. Jason removes his mask, revealing his disfigured face and Chris recognizes him as the man who attacked her two years ago. Before Jason can kill Chris, Ali returns and attacks Jason, which finally results in his death, however, the distraction allows Chris to find an axe and strike Jason in the head with it, who collapses. Exhausted, Chris pushes a canoe out into the lake and falls asleep, waking in fright the next morning. She sees Jason in the barn and tries to escape as he comes after her, but it all turns out to be a hallucination. As she calms down, the decomposing body of Pamela Voorhees emerges from the lake and grabs her, dragging her into the water, which turns out to be another hallucination (a scene replicated from the end of the first film, but with Pamela instead of Jason).
Later, police escort a clearly disturbed and hysterical Chris from Higgins Haven, stating that she was deeply shaken by the deaths of her friends. As she is driven away, Jason's body is shown lying in the barn and the lake seems to be once again at peace.

Question: Who kills Harold and his wife?
Answer: Jason.