Los Angeles ? Police believe a 72-year-old insurance claims adjuster arrested earlier this month is the most prolific serial killer in the city’s history, having raped and strangled as many as 30 older women over two decades.

The break in the cold case came in October when John Floyd Thomas Jr., who had twice been convicted of sexual assault, had a DNA sample taken as part of an effort to build an offender database.

Thomas was charged April 2 with murdering 68-year-old Ethel Sokoloff in 1972 and 67-year-old Elizabeth McKeown in 1976, both of whom were sexually assaulted and strangled. DNA matching Thomas’ was found at three other crime scenes in the 1970s and ’80s, police robbery-homicide Capt. Denis Cremins said.

Detectives now consider Thomas a suspect in at least 25 other killings, and the number could grow as detectives probe unsolved cases going back to the 1950s, Cremins said. It could not immediately be determined where the other killings took place.

“If he turns out to be the guy, he probably would be the largest ever (serial killer) in the city of Los Angeles,” Cremins said.