MONROE — The attack in 2015 was vicious, quick and deadly.

Late that May afternoon within the Special Offenders Unit of the Monroe Correctional Complex, one inmate was led off in handcuffs; the other whisked away to a hospital in a coma from which he would never wake. Both had histories of mental illness.

A federal lawsuit that followed delved into questions about the oversight and custody classification of the attacker, a convicted killer whose delusional thoughts concerned corrections officers and mental health workers alike. Many feared that Benjamin Cory Price’s behaviors were escalating in the days, weeks and months before he beat and stomped to death Gordon “Casey” Powell, 45. The victim had been described in court papers as “the smallest and frailest” of the offenders in his unit. Price was 10 years younger, 7 inches taller and more than 60 pounds heavier than Powell.

The assault lasted just nine seconds and occurred within a few feet of a corrections officer.

The lawsuit came to an end last week with a $1.5 million settlement hammered out between attorneys representing workers at the prison and Powell’s estate.

“It was our allegation that there were multiple failures on the part of the (state) Department of Corrections with regard to both corrections officers and psychological staff,” said Seattle attorney Edwin Budge, whose firm filed the lawsuit. “These were people who had information that would have led them to believe that Price was an extraordinarily dangerous person to be housed in this relatively low-security unit.”

Jeremy Barclay, a spokesman for the corrections department, confirmed a $1.5 million settlement was reached Monday.

“When making the determination to settle the case, the department assessed and managed the risks facing the agency and acted in the best interest of the state,” Barclay said. “The settlement does not indicate an admission of liability.”

Price was charged in Snohomish County Superior Court with aggravated first-degree murder. The killing was recorded by prison surveillance cameras. The criminal case has been dismissed for now while he receives treatment at Western State Hospital. The charges can be refiled if Price is ever deemed competent to stand trial.

Price has a long history of violence fueled by psychotic thoughts. In two fatal attacks, he told authorities he believed his victims were demonic. In a third attack, during which he tried to strangle a cellmate with strips of bed sheet, he allegedly claimed his victim was the devil and he had to kill him to protect himself and his daughter.

As a teen, Price assaulted another young man with a baseball bat, fracturing his skull.

In 2008, Price was charged with murder, roughly 17 months after 44-year-old Dawn Ruger disappeared in Skagit County. Price eventually confessed and led detectives to a shallow grave along a creek bed in eastern Whatcom County. Acquaintances said Price had been acting strangely around the time Ruger vanished and was calling himself Archangel Michael, a biblical figure who waged war with Satan.

Price’s sanity was a question for the court. He pleaded guilty to manslaughter and received a 12-year sentence.

Less than a year into his prison sentence, while assigned to general population at Stafford Creek Corrections Center near Aberdeen, Price tried to strangle his new cellmate — again invoking a fear of the devil as his explanation.

Grays Harbor County prosecutors declined to file charges. They reasoned that the assault appeared to be the result of mental health issues and that the victim was not injured.

“Prosecution in a case like this is going to cost a substantial amount of county and state resources to deal with the mental health issue,” a letter declining prosecution stated. “The Department of Corrections has the ability to monitor this offender’s behavior and punish him through their infraction system.”

As a result, a potential “third strike” felony that could have placed Price in prison for the rest of his life and likely in close observation for at least four years, became an internal issue for the prison system.

Price was transferred to the Special Offenders Unit for mentally ill offenders in Monroe. He spent 14 months under tighter security before being promoted to medium custody and moved to a least-restrictive unit.

On six occasions after that, Price was removed from his living unit and placed in a Close Observation area until his symptoms improved.

Thirteen months before the attack, a unit psychologist wrote that Price had delusional beliefs about the FBI and “demonic psychological intrusions,” and noted that Price “has murdered while operating under delusional beliefs,” according to court papers.

That psychologist instructed a mental health counselor that he should never be alone with Price. The counselor would later say that Price “had the potential to quickly become violent and seriously hurt (me)” as well as offenders.

For months, Price had described delusions that he was a trained contract killer acting under orders. His diagnosis was paranoid schizophrenia and antisocial personality disorder.

Corrections officers also expressed concern multiple times, according to court papers.

For instance, on the day of the attack on Powell, a corrections officer noted in an operations log that Price seemed agitated and “off baseline.” That terminology would alert her colleagues and, she hoped, would lead to Price being assessed by a mental health counselor.

After her brother’s death, Stephanie Powell Leisure and her father, Gordon Clay Powell, wanted answers. Years before Gordon Powell’s death, she’d become his legal guardian. A judge had declared her brother “an incapacitated person.” He slept on the couch at her home for many years.

Powell Leisure brought the lawsuit to try to find out what happened to her brother and if his death could have been prevented. An initial report from a team of Department of Corrections supervisors left too many questions unanswered.

Her search for answers led her attorneys to file multiple records requests and to depose many witnesses connected to the prison and police investigation.

Powell had ended up in the Monroe prison in 2014. He broke a window to a distillery in Centralia and stole four bottles of liquor. Six hours later, police were called to a pharmacy in town to deal with a man sitting on the ground showing signs of “severe intoxication.” It was Powell. When the officer attempted to arrest him for trespassing, Powell grabbed his wrist and began to lay down. Powell was charged with burglary and assault.

For Budge, Powell’s death was a classic case of missed warning signs.

“The entire system failed Casey. There were no winners here,” Budge said. “Stephanie lost her beloved brother. Clay lost his beloved son. Casey lost his life and taxpayers lost $1.5 million. All we can hope is this type of preventable tragedy won’t happen again.”