Updated

Murder charges have been filed against a sergeant accused of killing four other soldiers and a Navy officer in May 2009 at a mental health clinic in Iraq, the Army said Friday.

The charges against Sgt. John Russell were referred Wednesday and announced Friday in a statement from Joint Base Lewis-McChord. He faces five charges of premeditated murder, one of aggravated assault and one of attempted murder.

If convicted, he could face the death penalty.

The charges result from an investigation into the shooting at the Camp Liberty Combat Stress Center near Baghdad.

No date for the court-martial has been set. Russell is being held at the base about 40 miles south of Seattle.

Russell is from Sherman, Texas, and is now about 47 years old, said Lt. Col. Gary Dangerfield. The delay since the incident has been filled with the process of determining whether Russell is fit to stand trial.

Russell has an Army defense attorney but it is standard procedure for them not to comment to the media, Dangerfield said.

The shooting was one of the worst instances of soldier-on-soldier violence in the Iraq war and raised questions about the mental health problems for soldiers caused by repeated tours of duty.

"I don't know of any other worse blue-on-blue in Iraq," Dangerfield said.

A hearing on possible charges was held in August 2009 at Fort Leavenworth, Kan. Two evaluations presented during that hearing said Russell suffered from severe depression with psychotic features and chronic post-traumatic stress disorder. A March 2011 evaluation said the major depression with psychotic features was in partial remission.

Russell was nearing the end of his third tour when his behavior changed, members of his unit testified in 2009. They said he became more distant in the days before the May 11, 2009, attack, and that he seemed paranoid that his unit was trying to end his career.

On May 8, Russell sought help at a combat stress clinic at Camp Stryker, where his unit was located. On May 10 Russell was referred to the Camp Liberty clinic, where he received counseling and prescription medication to treat his symptoms.

Witnesses said the following day they saw Russell crying and talking about hurting himself. He went back to the Camp Liberty clinic, where a doctor told him he needed to get help or he would hurt himself. Russell tried to surrender to military police to lock him up so he wouldn't hurt himself or others, witnesses said.

Military prosecutors say Russell left the clinic and later returned with a rifle he took from his unit headquarters and began firing. He was arrested afterward.

Killed in the shooting were Navy Cmdr. Charles Springle, 52, of Wilmington, N.C., and four Army service members: Pfc. Michael Edward Yates Jr., 19, of Federalsburg, Md.; Dr. Matthew Houseal, of Amarillo, Texas; Sgt. Christian E. Bueno-Galdos, 25, of Paterson, N.J.; and Spc. Jacob D. Barton, 20, of Lenox, Mo.

Russell deployed to Iraq with the 370th Engineer Company, 54th Engineer Battalion from Bamberg, Germany. In Iraq the 54th was assigned to the 555th Engineer Brigade, based at Lewis-McChord, which is responsible for the court martial.