The Federal Bureau of Investigation is offering a $50,000 reward for tips on a serial killer in a 40-year-old cold case. The killer is suspected of murdering 12 people and raping 45 others throughout California from 1978 to 1986. The suspect, dubbed the Golden State Killer by authorities, had a particularly brutal modus operandi: He’d sneak into the bedrooms of couples late at night and tie the man up before raping the woman. Sometimes he would simply kill the couples, authorities said. It is not clear what prompted investigators to step up their efforts now, but a spokeswoman for the FBI said it is an “ideal time” to try to get people to come forward if they know anything about the man. He is described as a white male with blond or light-brown hair, thought to be between 60 and 75 years old.