EVERETT — The attack that killed a Centralia man lasted just nine seconds.

Now, a Monroe prisoner with a long history of mental illness is charged with aggravated murder for the homcide.

Benjamin Cory Price, 35, is accused of stomping another inmate to death inside the Special Offender Unit at the Monroe Correctional Complex. Gordon Powell, 45, died about a week later, from “immediately devastating trauma” to the brain. The May 9 attack was caught on the prison’s video surveillance system.

Price allegedly confessed to the slaying, saying he’s been training as a government assassin since the age of 4. He called Powell a “Satan buddy.” He also said Powell used telepathy to tell him that if he assaulted him, Price would finally get to talk to police and a lawyer.

“Told everyone I need to talk to law enforcement. I’m getting desperate enough to kill someone,” Price allegedly said to corrections officers after the assault.

Snohomish County deputy prosecutor Chris Dickinson earlier this month charged Price with aggravated murder. Under the law, killing someone inside a prison can be considered an aggravating factor. The inmate is expected to be arraigned Aug. 5.

Snohomish County Prosecuting Attorney Mark Roe will have to decide after that hearing whether he’ll seek the death penalty for Price.

The inmate already is serving a 12-year sentence for another killing. Price strangled his girlfriend, Dawn Ruger, in 2006 and hid her body in rural Whatcom County. Two years later he confessed to the killing and led police to her body. Price claimed Ruger was putting demons in his head. He was charged with second-degree murder in Skagit County and eventually pleaded guilty to manslaughter after a lengthy stay at Western State Hospital.

Price also made delusional claims in 2011 after attempting to strangle his cellmate at Stafford Creek Correctional Center in Grays Harbor County. He said he had a dream convincing him that his new cellmate was the devil. He wrapped a bedsheet around the man’s neck but wasn’t able to follow through. He never faced any criminal charges for that assault.

In Monroe, Price was housed in the prison’s mental health unit. The assault happened as Powell was walking back to his cell from dinner. Price allegedly charged the man and knocked him to the ground with a single punch. He is eight inches taller than Powell and outweighed him by about 40 pounds. Powell was on the floor as Price reportedly kicked him and stomped on his head. Powell was only able to cover his head.

He was unresponsive when corrections officers reached him. He had traumatic brain swelling that doctors could not reverse. He died May 18.

The Centralia man was serving time for second-degree burglary. He had broken a window at a store and taken some liquor. An internal investigation at the prison is under way.

Diana Hefley: 425-339-3463; hefley@heraldnet.com. Twitter: @dianahefley.