Story highlights Army Sgt. John Russell admitted to the May 11, 2009, killings in Iraq

Russell, 48, told the court he "did it out of rage," The News Tribune of Tacoma reported

A May 6 hearing has been scheduled to determine whether the killings were premeditated

A U.S. Army sergeant pleaded guilty Monday to gunning down five fellow service members at a combat stress clinic in Iraq after military prosecutors agreed not to seek the death penalty.

Sgt. John Russell admitted to the May 11, 2009, killings at Baghdad's Camp Liberty, telling a Joint Base Lewis-McChord court that he "did it out of rage," according to The News Tribune of Tacoma.

The court scheduled a May 6 hearing to determine whether Russell committed the slayings with premeditation, which the 48-year-old soldier has disputed. The outcome will determine whether Russell is sentenced to life without parole or given a lesser sentence.

As part of the plea agreement, Russell described to the court how he killed Navy Cmdr. Charles Springle, Army Maj. Matthew Houseal, Sgt. Christian Bueno-Galdos, Spec. Jacob Barton and Pfc. Michael Yates Jr.

It was the first time Russell has publicly detailed what happened at the combat stress clinic.

Russell, a communications specialist, was on his third deployment to Iraq.

His attorneys have argued Russell suffers from post-traumatic stress disorder, depression and a brain injury from previous combat, which make him not fully responsible for the killings.