Updated

The U.S. Army sergeant who has been charged with murder and aggravated assault in the fatal shooting of five fellow soldiers at Baghdad's Camp Liberty was due to leave Iraq soon after three tours.

Sgt. John M. Russell was taken into custody outside the military counseling clinic following Monday's shooting at Camp Liberty, said Maj. Gen. David Perkins. It was the deadliest case of soldier-on-soldier violence since the Iraq war began in 2003.

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Perkins gave few details of the shooting and said there were conflicting accounts of what happened.

He said Russell was referred to the clinic by his superiors, presumably because of concern over his mental state.

Perkins said the assailant's weapon had been taken away, but somehow he got a new gun, entered the clinic and opened fire.

In Washington, a Pentagon official said Russell was escorted to the clinic, but once inside argued with the staff and was asked to leave. After he and his escort drove away, Russell apparently seized the escort's weapon and returned to the clinic, said the official, speaking on condition of anonymity because the investigation was ongoing.

Russell is on his third tour of duty in Iraq, according to his service record. He was due to go home in three weeks, the official said.

Excerpts of the service record, obtained by The Associated Press, show that Russell previously did two one-year tours of duty here, one starting in April 2003 and another beginning November 2005.

Russell's hometown was listed as Sherman, Texas, when he enlisted. He entered the Army National Guard in 1988 and served until 1994. Russell became an active duty soldier in 1994, the record shows.

It also says Russell served in Serbia through the last half of 1996 and Bosnia and Herzegovina in the last half of 1998.

Russell received several medals and commendations, which an official described as typical for Russell's rank and time in the military. The official spoke on condition of anonymity because he wasn't authorized to speak on the record.

Russell has no criminal record in Texas except for a conviction for criminal trespassing in 1988, according to Department of Public Safety Records.

No one answered the door Tuesday at the one-story brick home that records indicate is owned by Russell's parents. The house, located in an unincorporated area of Grayson County several miles outside Sherman, not far from the Oklahoma border.

A man who answered the phone listed for Russell's ex-wife and 20-year-old son declined to identify himself and said "No comment."

Perkins said two of the dead were officers from the 55th Medical Company, a reserve unit from Indianapolis. The others were enlisted personnel seeking treatment at the clinic. He did not identify the victims by name.

Russell, of the 54th Engineer Battalion based in Bamberg, Germany, was charged with five counts of murder and one count of aggravated assault in Monday's shooting, Perkins said.

He said a probe has also begun into whether the Army has enough mental health facilities in Iraq, where the attack at Camp Liberty has drawn new attention to the issue of combat stress and frequent deployments to battle zones.

The U.S. military is coping with a growing number of stress cases among soldiers in Iraq and Afghanistan — many of whom are on their third or fourth combat tours. Some studies suggest that about 15 percent of soldiers returning from Iraq suffer from emotional problems.

"One thing if we've learned from this war, we learned from World War II, Korea, Vietnam, the previous wars, is not all injuries are physical," said Maj. Gen. Daniel P. Bolger, commander of Multi-National Division-Baghdad.

President Barack Obama, who visited an adjacent base last month, said in a statement that he was "shocked and deeply saddened" by the report.

At the Pentagon, Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, said the shooting occurred "in a place where individuals were seeking help."

"It does speak to me about the need for us to redouble our efforts in terms of dealing with the stress," Mullen said.

Violence has dropped sharply in Iraq since the high point in 2007, but attacks continue, especially in the north.

Also Tuesday, a suicide bomber rammed his car into an Iraqi police truck in the northern city of Kirkuk, killing five policemen and a civilian.

Kirkuk is the center of Iraq's oil production in the north and is contested between its Kurdish, Turkomen and Arab populations.