A California prison inmate confessed in a letter that he beat two child molesters to death with a cane while behind bars just hours after his urgent warning to a counselor that he might become violent was ignored, a newspaper chain reported Thursday.

Jonathan Watson, 41, confessed in the letter to the Bay Area News Group in Northern California that he clubbed both men in the head on Jan. 16 at the California Substance Abuse Treatment Facility and State Prison in Corcoran.

Prisoner David Bobb, 48, died that day. Graham De Luis-Conti, 62, died three days later at a hospital. Both were serving life sentences for aggravated sexual assault of a child under 14.

“We can't comment on an active investigation," Dana Simas, spokesman for the California Department of Corrections and Rehabilitation, wrote in an email.

Watson is serving a life sentence for a 2009 murder conviction.

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Days before the attack, he said his security classification was changed and he was transferred from a single-person cell to a lower-security dormitory pod at the Central Valley facility. Watson called the switch a “careless" mistake and said he had protested the decision.

Watson wrote that six days after he arrived at the prison, a child molester moved into the pod. Watson believed the man began taunting other inmates by watching children's television programming. Watson said in the letter he couldn't sleep that night “having not done what every instinct told me I should’ve done right then and there."

Two hours before the attacks the next day, Watson told a prison counselor that he urgently needed to be transferred back to higher-level security “before I really (expletive) one of these dudes up,” but the counselor “scoffed and dismissed" him.

Watson said he returned to his housing pod.

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“I was mulling it all over when along came Molester #1 and he put his TV right on PBS Kids again,” he wrote, according to the newspaper chain. “But this time, someone else said something to the effect of ‘Is this guy really going to watch this right in front of us?’ and I recall saying, ‘I got this.’ And I picked up the cane and went to work on him.”

Watson said he then left the housing pod to find a guard and turn himself in, but on the way, he saw “a known child trafficker, and I figured I’d just do everybody a favor,” Watson wrote. “In for a penny, in for a pound.”

Watson said he then told a guard, who didn't believe him “until he looked around the corner and saw the mess I’d left in the dorm area,” Watson wrote.

Watson is in segregated housing while he is under investigation for the killings. He hasn't been charged yet.

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“Being a lifer, I’m in a unique position where I sometimes have access to these people and I have so little to lose,” Watson wrote. “And trust me, we get it, these people are every parents’ worst nightmare."