SACRAMENTO, Calif. -- Angelo Buono Jr., whose gruesome killing of young Los Angeles women in the 1970s earned him the nickname "Hillside Strangler," died Saturday in prison, corrections officials said.

Buono, 67, was found dead at Calipatria State Prison, said Bob Martinez, a spokesman for the state Department of Corrections.

The cause of death was not immediately known but Martinez said Buono suffered from heart problems. There were no signs of trauma, and Buono was alone in his own cell when he died.

"He had assigned duties at the prison, and he was singled-celled because of the nature of his crime," Martinez said. "There was nothing exceptional about his conduct in prison."

In November 1983, Buono was sentenced to life in prison without the possibility of parole after being convicted of killing nine young women and dumping their nude bodies on Los Angeles-area hillsides, earning him the nickname "Hillside Strangler."

His adoptive cousin, Kenneth Bianchi, pleaded guilty to five of the murders and testified against Buono. Bianchi is serving his prison sentence in Washington state, where he killed two other women.

The two were accused of kidnapping, raping, torturing and killing the women, ranging in age from 12 to 28, during a four-month period in 1977 and 1978.

Authorities said Buono and Bianchi would pose as police officers while driving at night, pull over unsuspecting woman drivers, then abduct them and take them to Buono's suburban home. The bodies were disposed of on the wooded hillside not far away.

In 1986, Buono took a wife while behind bars, marrying Christine Kizuka, a mother of three and supervisor at the Los Angeles office of the state Employment Development Department.