Susan Atkins, one of madman Charlie Manson‘s cult of Helter Skelter thrill killers, is dead.

Atkins died from brain cancer at 61 at the Central California Women’s facility in Chowchilla on Thursday night, Terry Thornton, spokeswoman for the state Department of Corrections and Rehabilitation, confirmed.

In 1969 Atkins joined Manson’s band in a series of killing that shocked America.

Atkins had confessed to killing the wife of director Roman Polanski, pregnant Sharon Tate, who was hanged and stabbed 16 times.  Tate’s full-term fetus died with her.

The very next night, Atkins accompanied Manson and his followers when they slaughtered Leno and Rosemary LaBianca.

"She was the scariest of the Manson girls," said Stephen Kay, who helped prosecute the Manson cases with chief prosecutor Vincent Bugolsi

Kay argued vehemently against Atkins’ release at her parole hearings. "She was very violent."

Atkins broke open the case against Manson when she bragged of her participation in the slayings to cellmates at Sybil Brand Institute in East Los Angeles, where she was being held on other charges.

Two cellmates told authorities of her confession.

After prosecutors cut a deal, promising to not to seek the death penalty against her, Atkins appeared before a grand jury, providing information that led to her own indictment, as well as that of Manson and others.

Later, in a lurid 10-month trial, she provided key testimony that landed Manson behind bars.