Juan Corona, one of the most active serial killers in the United States before he was convicted in 1971, died Monday at age 85. He had been serving 25 concurrent life sentences at the time of his death.

Corona, incarcerated in Corcoran, California, was convicted of killing – and burying – the bodies of 25 California farm laborers. He had been moved to an undisclosed hospital, Vicky Waters of the state Department of Corrections and Rehabilitation reported, where he eventually died.

Many of the workers he killed, usually via stabbing, were actually hired by Corona. He later buried their bodies in shallow graves along the Feather River, north of Sacramento. He killed one of his victims with a gunshot wound to the head.

PENNSYLVANIA CONVICTED MURDERER IS SUSPECTED SERIAL KILLER, POLICE SAY

Corona was arrested after a peach farmer who had contracted with him for hired pickers became suspicious on finding a hole that had been freshly dug and then quickly filled in.

The farmer called authorities, suspicious someone was burying garbage in his orchard. Instead they found the body of a man whose head had been hacked and his torso riddled with stab wounds.

Corona was arrested a week later and subsequent searches turned up the bodies of 24 more people, including several Corona had recruited for farm work.

In 1978 an appeals court overturned Corona's conviction, ruling he had received incompetent representation from his attorney. He remained jailed while he was re-tried and was convicted again in 1982 on the same 25 counts. He would go on to have his parole denied eight times - most recently in 2016.

A stabbing he suffered in 2017 almost left him dead, but he survived minus sight in his left eye.

CLICK HERE TO GET THE FOX NEWS APP

"It was a gruesome manner of killing. He hacked these people to death," Sutter County District Attorney Amanda Hopper told The Associated Press after attending Corona's last parole hearing.

The Associated Press contributed to this report.