A judge sentenced a 36-year-old man on Friday in Seattle to 25 years in prison for an attack on a King County corrections officer in January 2011 at the Maleng Regional Justice Center in Kent.

Sean L. Graham, received an exceptional sentence beyond standard range of 17 to 23 years from King County Superior Court Judge Theresa Doyle for the first-degree assault at the county jail, according to the King County Prosecuting Attorney’s Office. Prosecutors asked for 30 years in prison based on the aggravating circumstances.

Graham knocked corrections officer Gil Letrondo unconscious during the assault. The guard was on the floor when Graham stomped on his neck and chest.

A jury in November found Graham guilty of first-degree assault as well as three counts of custodial assault for assaulting other officers who were trying to subdue Graham.

The jury also found aggravating circumstances that the unconscious guard was a vulnerable victim and that he was a law enforcement officer performing his official duties at the time of the attack.

At the time of the assault four years ago, Graham was in custody to face a 2009 first-degree robbery charge. He was later transferred to the county’s high-security facility in downtown Seattle.

According to charging papers, Graham reportedly was upset at Letrondo for not allowing him his hour out of the cell after the inmate had threatened the officer and called him names.

Letrondo on the next day entered a unit to relieve another guard. Graham also was in the unit taking a shower. When the two officers were talking, Graham quickly approached Letrondo and punched him in the face. The inmate and two guards separated briefly before Graham charged Letrondo again, punched him in the face and knocked him into a wall.

Letrondo fell backwards, hit his head on a metal-framed window and was knocked unconscious.

Graham then continued to go after Letrondo, who had fallen unconscious, and stomped on the officer’s body at least three times in the body, neck and spine.

Paramedics transported Letrondo to Harborview Medical Center in Seattle, where he remained for two days to be treated for a variety of injuries to his body, including a blood clot inside his skull.

One officer told investigators that he believes Graham had planned the attack and if given the chance would have killed Letrondo.

Four other officers also were injured when they came to the aid of the fallen officer. One of the officers was treated at Valley Medical Center in Renton for cuts to his face and neck and a hand injury.

Three other officers also sustained injuries to either their hands or legs when Graham refused orders to stop fighting and continued to resist the guards. The fight lasted about five minutes.

When officers later searched Graham’s cell, they discovered a letter Graham wrote earlier in the month to his mother that read in part, “I’ve been insanely angry for the past few weeks. Very, very ready to kill them doctors, lawyers, guards and every inmate in my sight. Truly I can relate to a wild animal.”

According to charging papers, Graham has prior convictions for second-degree arson (2006), third-degree assault (1997 and 1998) and felony harassment (1998). He also has misdemeanor convictions for harassment and fourth-degree assault between 2004 and 2007. Graham has a long history of mental illness and has been committed to Western State Hospital in Tacoma and Fairfax Hospital in Kirkland at least five times since 2006.