The House On Sorority Row (1983)

Eric Slater actually survived his birth but was left with serious certain abnormalities from birth defects. After doing in a drunken reveler of a house party (by giving him a bloody tracheotomy with Mrs. Slater's cane) Eric then uses his mum's cane on the rest of the sorioty girls (one of whom, Jeanie loses her head and has it dumped in a toilet) until only Katy is left. Dr. Beck shows up and convinces her to set up a sting with him to ensnare Eric and thus subdue Eric but ends up shooting Katy's blind date Peter with a tranquilizer as he is coming in through some patio doors, which ensures Eric is able to get the drop on Doc and hack him up instead. He then traps Katy in the attic with him having concealed himself by slipping into a clown outfit to stand right next to her. He lashes out with his mom's cane but she distracts him by knocking over some objects enabling her to stab him with a concealed knife repeatedly before dropping him through the attic hatch onto the floor far below. Katy lays on the floor, believing her nightmarish ordeal is over. She's unaware that Eric has opened his eyes below her...