The Marin County coroner's office told the Los Angeles Times Ramirez, who was on California's death row for killing 13 people but was suspected of other slayings, died June 7 while being treated at Marin General Hospital in Greenbrae.
Ramirez had been imprisoned at the San Quentin prison.
"This person hurt many people, and our thoughts should be with the next of kin and survivors of these senseless attacks," LA Deputy District Attorney Alan Yochelson, who prosecuted Ramirez, said.
Easer Egg Roll brings thousands to White House
Lytro unveils camera that can focus a photo after shooting it