BAGHDAD, Iraq (CNN) -- The U.S. soldier who authorities say killed five fellow troops -- including a Navy commander -- at a stress clinic in Iraq on Monday apparently used a weapon he wrested away from another soldier, a Defense official said.
The Camp Liberty shooter has been identified as Army Sgt. John M. Russell of Sherman, Texas.
After getting the weapon, the soldier stole a military vehicle and drove to the clinic, where earlier he had been in a fight, the official said.
The shooter was identified as Army Sgt. John M. Russell, according to Maj. Gen. David Perkins, the military spokesman who briefed reporters in Baghdad, Iraq, on Tuesday.
Russell has been charged with five counts of murder and one count of aggravated assault after the shooting at Camp Liberty, near Baghdad's international airport, Perkins added. Watch how the Army is handling the case »
A 44-year-old communications specialist from Sherman, Texas, Russell is serving his third tour in Iraq and has previously deployed to Bosnia and Kosovo, according to his service record.
His father, Wilburn Russell, also of Sherman, said Russell had e-mailed his wife saying he believed unidentified officers were trying to run him out of the military.
"As far as he was concerned, the military was the most wonderful thing that ever happened to him," Wilburn Russell said. "Evidently, he felt they turned against him and life was over. He didn't care any more, I guess.
"He broke. He just couldn't handle it."
Russell had recently been referred to counseling by his commander because of unspecified words and actions, Perkins said. The commander also ordered that the sergeant's weapon be taken away.
Among those killed in the shooting was Navy Cmdr. Charles Springle, 52, of Wilmington, North Carolina. Springle was part of the 55th Medical Company, stationed at Camp Liberty.
The military had not released the names of the other victims Tuesday afternoon, pending notification of their families.
A senior Defense official told CNN that when Russell was leaving the clinic Monday, he "became hostile and an altercation broke out."
He was then escorted back to his quarters by another soldier, said the official, who has read the most recent summary of the investigation in Baghdad.
A couple of hours later, Russell seized a weapon from a fellow soldier, "commandeered" a vehicle and drove back to the clinic, the Defense official said. A soldier from Russell's quarters called military police, but they weren't able to stop him in time.
A summary of the investigation earlier Tuesday had suggested Russell took the weapon from his escort -- but that was unclear in the most recent report.
The escort typically would have been a buddy, someone from Russell's unit, the Defense official said. Such steps are handled within the unit, and with the suicides of other troops they would have wanted someone close to keep an eye on him: "Keep your buddy close."
The aggravated assault charge is for the struggle for the weapon in the vehicle, another Defense official said.
Russell is from the 54th Engineering Battalion, based out of Bamberg, Germany -- a unit attached to Multi-National Division South but based at Camp Victory in Baghdad. He's now in military police custody at Camp Victory.
The 54th's 15-month deployment began in May 2008; the battalion is due to leave Iraq in August.
Perkins said the military has launched a criminal investigation into the attack and another probe to explore the military's mental health services operations and how such an incident can be avoided in the future.
Among the five killed, two are officers from the staff of the clinic -- one from the Army and the other from the Navy. Both are from the 55th Medical Company. The other three were enlisted soldiers who happened to be at the clinic.
Perkins, who said there are no immediate insights on a motive, said Russell had been receiving counseling within his battalion. Last week, Russell was referred to the Camp Liberty center.
"He had been seen by his chain of command, chaplain, things like that for about the week prior to (the incident), but that could have been the first time he physically had gone to the clinic," Perkins said.
"He was referred to counseling the week before and his commander determined that it was best for him not to have a weapon," he explained. Watch how the shootings have raised the issue of post-traumatic stress disorder »
Perkins could not confirm any sequence of events and said the investigation into the incident is ongoing.
"Speculation does not serve us well, or rumor," he said. "We need to know the facts because we will spend a lot of time trying to prevent these types of things in the future."
The clinic is temporarily closed for the investigation, with alternate locations available, Perkins said.
Russell was apprehended outside the clinic after the shots were heard, Perkins said.
Maj. Gen. Daniel Bolger, the commander of Multi-National Division-Baghdad, also spoke to reporters, telling them that a "tragedy like this" points to the "challenges" troops face.
"When something like this happens we've got to be careful not to judge too harshly and extend a sympathy that is due to all these soldiers and families," he said.
Bolger said there is a "stigma" to mental health issues.
"Not all injuries are physical, and so you've got to have that door open for the guys, and that is one of the things we emphasize in our training. And, it's particularly challenging for a fellow like Sgt. Russell.
"He is a non-commissioned officer. ... He is in a leadership capacity. And to make that trip down there is a tough decision for either him or his chain of command to make, but we are willing to make it and we have had those facilities and care available."
Wilburn Russell said he hopes his son is found to be temporarily insane.
"We're devastated," he said. "We're heartsick, not just for our son, but for the people that are involved -- the people that got killed and their families.
"My gosh, it's a horrible thing. It's impacted hundreds of people."
CNN's Jomana Karadsheh, Mike Mount, Chris Lawrence, Barbara Starr, Cal Perry and Ed Lavendera contributed to this report