Young Boy Possessed by Dead Father Killed by His Mother

by Barbara
(New York, New York, USA)

I'm trying to remember the title of a 70's or early 80's film about a young boy who's mother killed his father to marry someone else.

The boy winds up getting possessed by his dead father, torments and kills his mother and stepfather.

In one scene, the mother frantically looks for her son. When she finds him, she calls him to come to her. He runs to her and hugs her, then turns into his dead father. A dresser is moved by the spirit and the mother's throat gets slit.

In aonther earlier scene, the boy sees his mother and stepfather having sex and says 'pigs'.

Any ideas?