On the plus side, David McBee has a fiancee who stuck by him, a 2-year-old son who loves him. They've helped him persevere through dark times — blackouts, anger, confusion — as he struggles with the invisible wounds of his combat duty in Iraq.

As a Marine, McBee engaged in the initial assault on Iraq from Kuwait in 2003 and the often-chaotic battle of Fallujah in late 2004.

He returned to the United States in 2005, worked for a time with the postal service and got engaged. His fiancee, Audra Cardoza, gave birth to a son in 2006.

About a year after his return, McBee began to notice a change in his personality, including what he describes as "blackouts" — periods of time he couldn't account for.

"One day, me and my buddies and fiancee, we went out and started drinking," he said. "I had a meltdown. ... All this stuff that was in my head that I'd never said to anybody started coming out. I couldn't stop crying."

The "stuff" included images of Fallujah residents, children among them, killed by his own unit as it swept through neighborhoods that were supposed to have been evacuated.

"We search houses. We see people in there — they're not supposed to be there. They're considered hostile. We just opened fire," he said.

"We saw a little kid in the middle road. There was no stopping the convoy. We ran him over."

McBee's condition worsened in June, after a friend and fellow veteran committed suicide. He checked into a veterans homeless shelter in Leeds, Mass., and was diagnosed with post-traumatic stress disorder as well as alcohol dependence. He has suffered migraines, hearing loss, various back and shoulder problems.

At the shelter, McBee befriended Army Spc. Andrew Cotrel, also suffering PTSD linked to Iraq combat duty in 2003.

"My first day, Andrew was there. Two different parts of Iraq, two different things going on, and we had so many similarities," McBee said. "As a vet, you can just sit down and talk. You have something in common, doesn't matter where you were, what you did. You know you both served."

They're among about 1,500 veterans of the Iraq and Afghanistan wars identified by the Department of Veterans Affairs as experiencing homelessness. The 120-bed Leeds shelter, run by a nonprofit called Soldier On, serves a handful of veterans who fought in those two wars, mixed with dozens who served in Vietnam.

The mission, says Soldier On, is to assist veterans with "picking up the pieces of their lives."

In August, McBee, now 24, moved in with Cardoza and their son, Aiden, in a small apartment in nearby Chicopee. He plans to enroll soon in six-week VA inpatient PTSD treatment program.

Aiden, says McBee, is the "best thing ever."

"For a while, I didn't think anybody really cared for me — I didn't care about myself, so why would anybody else," he said. "To see him running up, his arms out, big smile, 'Daddy, Daddy, Daddy,' It's great."