Richard Ramirez, the convicted serial killer and rapist known as the Night Stalker, died Friday morning.

Ramirez was convicted of 13 murders that terrorized Southern California in 1984 and '85, and sentenced to death. He was awaiting execution when he was taken to Marin General Hospital.

Lt. Sam Robinson, an official for San Quentin State Prison, confirmed the death. Ramirez was 523. His cause of death was still being debated. The Department of Correctinos said that his death may have been due to natural causes but Hepatitis C could have claimed the killer's life TMZ reported Friday. The disease is contracted through IV drug use, blood transfusions and possibly sexual contact.

Ramirez became a household name in the mid 1980's when women were being raped and murdered. The killings were marked by Satanic symbols left at murder scenes and some victims were forced to "swear to Satan" by the killer. Ramirez would entered homes through unlocked windows and doors, thus the Night Stalker nickname being coined.

Some of his crimes included murdering a 29-year-old man in June of 1985 and then raping the victim's girlfriend who survived. The following month, Ramirez killed another man and forced the man's wife to perform oral sex on him. The cops were finally able to obtain a fingerprint and proceeded to release his mugshot to the public. Ramirez was caught in 1985 by East Los Angeles residents. They beat him when he attempted a carjacking.

During one of Ramirez' first court appearances, he raised a hand with a pentagram drawn on it and declared, "Hail, Satan." His trial lasted four eyes and was sentenced to death in 1989. The death sentence was appealed but in 2006, he California Supreme Court upheld Ramirez's convictions. The following year, the Supreme Court refused to hear the case.

In 2009, more evidence of Ramirez' other crimes became known. San Francisco police said DNA linked Ramirez to the April 10, 1984 murder of Mei Leung. She was 9 years old at the time she was killed in the basement of a residential hotel in San Francisco's Tenderloin neighborhood where she lived with her family.

Watch a jail house interview with Ramirez below.