Burial Ground: The Nights of Terror

Burial Ground original title Le Notti del terrore, also known as Nights of Terror, Zombi Horror, The Zombie Dead is an Italian grindhouse zombie movie directed by Andrea Bianchi. It is one of several films released under the alternate title of Zombie 3.

The group of people lock themselves in the mansion and, as night falls, the zombie siege begins. The first victim is Kathryn, the maid Anna Valente, who is pinned to a window and decapitated with a scythe. The zombies then begin to display unusually high levels of intelligence, using tools, axes to chop through doors, etc. One of the guests, George Roberto Caporali tries shooting at them with a shotgun but quickly runs out of shells.Zombies then break into the mansion and attack the guests in the library. One of the guests, the young Michael Peter Bark has become traumatized, and his mother Evelyn Mariangela Giordano tries comforting him in another room. Michael, however, seems to be becoming sexually attracted to his mother, and fondles her breasts while kissing her. Evelyn slaps him, and he runs off, screaming Whats wrong? Im your son Michael then encounters the nowzombified Leslie, another guest, and stands still and stares at her while she shambles towards him, snarling and covered in blood. ........

Source: Wikipedia