1976 Alice, Sweet Alice

Alice, Sweet Alice (1976), originally titled Communion, is a landmark American psychological slasher film directed by Alfred Sole. It is famous for being the film debut of Brooke Shields and is often cited as a prime example of an "American giallo" due to its stylish violence and religious themes.
Plot: Set in 1961 New Jersey, the story follows Alice (Paula Sheppard), a troubled 12-year-old girl who becomes the prime suspect when her younger sister, Karen (Brooke Shields), is brutally murdered at her First Communion by a figure in a yellow raincoat and a translucent mask.
Alternate Titles: The movie has been released under several names, including Communion (original title), Holy Terror (a 1981 reissue to capitalize on Shields' fame), and The Mask Murders.
Themes: It heavily explores Roman Catholicism, religious hysteria, sibling rivalry, and the disintegration of the American nuclear family.
Alice Spages: Played by Paula Sheppard (who was actually 18 at the time).
Karen Spages: Played by Brooke Shields.
Catherine Spages: Played by Linda Miller