An armed man arrested after police fired several shots at him in a Vista neighborhood apartment complex late Tuesday had served in Iraq and survived the war's single-deadliest attack on Idaho soldiers.

Boise police say George G. Nickel Jr., 38, was looking for his dog in his apartment building when he used an AR-15 rifle to try to shoot the locks off two different doors. Minutes later, Boise police say, officers confronted him in a stairway and fired an estimated 12 rounds at Nickel. Nickel didn't shoot back, police say, and no one was struck by any of the gunfire.

Nickel was one of 100 Idaho Army Reservists with the 321st Engineer Battalion who spent a year in Iraq in 2007. They had one of the most dangerous jobs there: hunting roadside bombs, the biggest killer of U.S. troops in Iraq.

Nickel suffered a broken leg and shrapnel in his face in a February 2007 attack that killed three Idaho soldiers. He recuperated at Walter Reed Army Medical Center in Washington, D.C., for about four months before returning to Boise, officials said then.

Boise police Chief Mike Masterson said his investigators are not sure why Nickel thought his dog was in his neighbors' apartment, why he used a rifle to try to shoot out the locks of two different doors, or why he pointed a handgun and flashlight at police.

"This is bizarre behavior," Masterson said Wednesday. "I don't know what would push people to that (level of) desperation."

SURVIVING THE WORST OF WAR

At the time of the Iraq attack, former KBCI-TV reporter Thanh Tan interviewed a soldier who had lived through a previous roadside bomb. She asked what Nickel would be going through as a lone survivor. Former Army Specialist Joel Coulter of Boise talked cautiously about the pain he said he and others go through.

"Three guys died. I survived. He (is probably) feeling depressed," Coulter said, referring to any soldier who survives an attack that others do not. "He's pissed. He's depressed, and right now he feels like he wants to die. For me, at least, it was like that."

A veteran suffering from post-traumatic stress disorder may not display any outward symptoms until a stressor such as job, family or other losses - even a lost dog - leads to a triggering event, said Dudley Blake, co-director of the PTSD Unit at the VA Medical Center in Boise. This break can occur years after the traumatic event. When this happens, a seemingly normal person can ramp up physiologically and emotionally, Blake said.

War alone can be traumatic enough, Blake said. Being injured and having three fellow soldiers killed can cause significant emotional and mental trauma, he said.

WHAT HAPPENED TUESDAY NIGHT

Police said Nickel, who lives on a lower level of the apartments in the 2600 block of Bedford Lane, went upstairs with an AR-15 rifle shortly after 11 p.m. and started pounding on an apartment door looking for his dog.

A witness called 911 about the time Nickel is accused of firing a bullet into the door and trying to kick his way into the apartment, police say. He shot twice more into another door, police say.

Responding officers confronted Nickel at the top of a stairwell.

They said Nickel pointed a handgun and flashlight at them and didn't drop them when ordered to. The officers fired at Nickel, and he took cover at the top of the stairwell, Masterson said.

That was when Nickel began talking to officers and surrendered.

Nickel was charged with felony counts of aggravated assault and discharge of a gun into an inhabited building; he was booked into the Ada County Jail Wednesday morning. He is scheduled to make his initial court appearance Thursday afternoon.

A task force led by the Ada County Sheriff's Office is investigating, as is routine when officers are involved in a shooting.

The four officers who fired at Nickel were placed on administrative leave, which also is routine. They were being interviewed Wednesday afternoon.

Boise community Ombudsman Pierce Murphy, who investigates when Boise police officers use deadly force, responded to the apartment complex to begin his investigation. His report will be issued after the task force review is complete.

Patrick Orr: 373-6619

Bethann Stewart and Cynthia Sewell contributed to this report.