(CNN)Joseph James DeAngelo, the suspected Golden State Killer, was charged Thursday with four additional counts of murder, according to Santa Barbara County District Attorney Joyce Dudley.
Suspected Golden State Killer now charged in 12 killings
Authorities have said they believe the Golden State Killer was responsible for killing a dozen people and for at least 50 rapes in 10 counties in California between 1976 and 1986.
DeAngelo, 72, who was arrested last month, was previously charged with eight slayings, including four in Orange County, two in Ventura County and two in Sacramento County. He has not yet entered a plea.
Prosecutors say each count of first-degree murder charges in Santa Barbara County comes with special circumstances and carries a maximum sentence of life in prison without the possibility of parole or the death sentence.
DeAngelo is accused of killing Debra Alexandria Manning on December 30, 1979, while committing a rape and a burglary, according to the new charges. He is also accused of killing Robert Offerman that same day while committing a burglary, according to the complaint.
DeAngelo is also charged with killing Cheri Domingo while committing a rape and a burglary and killing Greg Sanchez while committing a burglary -- both on July 27, 1981, according to the complaint.
"Violent cold cases never grow cold for victims or their loved ones," Dudley told reporters. "In fact, most of them spend their lives feverishly seeking answers and desperately hoping for justice."
DeAngelo's attorney Diane Howard said Thursday she was aware of the additional charges and added that they had been expected.
In recent years, there was renewed interest in the case. This year, a book and a series from HLN were released, in the hopes of shedding more light on the case.
Decades after the killings terrified communities throughout California, authorities tracked down the suspect by comparing genetic profiles from genealogy websites to crime scene DNA, according to investigators.
DNA from a crime scene was matched to genetic material from a relative who was registered on genealogy sites, and authorities later obtained a discarded sample of DeAngelo's DNA.
DeAngelo, a former police officer, Vietnam veteran and a mechanic, was a reclusive neighbor in Citrus Heights, a town about 16 miles northeast of Sacramento, according to residents.
He was being held in the Sacramento County Main Jail medical unit Thursday, Howard said.
"I'm not going to elaborate on why he's there -- his physical or mental state."
DeAngelo is scheduled to appear in a Sacramento County courtroom next week.
"I don't think he'll enter a plea yet," Howard said.