RAMADI, Iraq - He was 5 when he first fired an M-16, his father holding him to brace against the recoil. At 17 he enlisted in the Marine Corps, spurred by the memory of 9/11. Now, 21-year-old Galen Wilson has 20 confirmed kills in four months in Iraq — and another 40 shots that probably killed insurgents. One afternoon the lance corporal downed a man hauling a grenade launcher five-and-a-half football fields away. Wilson is the designated marksman in a company of Marines based in downtown Ramadi, watching over what Marines call the most dangerous neighborhood in the most dangerous city in the world. Here, Sunni Arab insurgents are intent on toppling the local government protected by Marines. Wilson, 5-foot-6 with a soft face, is married and has two children and speaks in a deep, steady monotone. After two tours in Iraq, his commanders in the 3rd Battalion, 8th Regiment call him a particularly mature Marine, always collected and given to an occasional wry grin. His composure is regularly tested. Swaths of central and southern Ramadi, 70 miles west of Baghdad, are dominated by insurgents who regularly attack the provincial government headquarters that Marines protect. During a large-scale attack on Easter Sunday, Wilson says, he spotted six gunmen on a rooftop about 400 yards away. In about 8 seconds he squeezed off five rounds — hitting five gunmen in the head. The sixth man dived off a 3-story building just as Wilson got him in his sights, and counts as a probable death. "You could tell he didn't know where it was coming from. He just wanted to get away," Wilson said. Later that day, he said, he killed another insurgent. Wilson says his skill helps save American troops and Iraqi civilians. "It doesn't bother me. Obviously, me being a devout Catholic, it's a conflict of interest. Then again, God supported David when he killed Goliath," Wilson said. "I believe God supports what we do and I've never killed anyone who wasn't carrying a weapon." He was raised in a desolate part of the Rocky Mountains outside Colorado Springs, "surrounded by national parks on three sides," he says. He regularly hunted before moving to Fort Lauderdale, Fla., as a teenager. His brother also serves in the military. Guns have long been part of Wilson's life. His father was a sniper in the Navy SEALS. He remembers first firing a sniper rifle at age 6. By the time he enlisted he had already fired a .50-caliber machine gun. "My father owned a weapons dealership, so I've been around exotic firearms all my life," said Wilson, who remembers practicing on pine cones and cans. "My dad would help me hold (an M-16), with the butt on his shoulder, and walk me through the steps of shooting." Technically, Wilson is not a sniper — he's an infantryman who also patrols through the span of destroyed buildings that make up downtown Ramadi. But as his unit's designated marksman, he has a sniper rifle. In the heat of day or after midnight, he spends hours on rooftop posts, peering out onto rows of abandoned houses from behind piles of sandbags and bulletproof glass cracked by gunfire. Sometimes individual gunmen attack, other times dozens. Once Wilson shot an insurgent who was "turkey peeking" — Marine slang for stealing glances at U.S. positions from behind a corner. Later, the distance was measured at 514 meters — 557 yards. "I didn't doubt myself, if I was going to hit him. Maybe if I would have I would have missed," Wilson said. The key to accuracy is composure and experience, Wilson says. "The hardest part is looking, quickly adjusting the distance (on a scope), and then getting a steady position for a shot before he gets a shot off. For me, it's toning everything out in my head. It's like hearing classical music playing in my head." Though Wilson firmly supports the war, he used to wonder how his actions would be received back home. "At first you definitely double-guess telling your wife, mom, and your friends that you've killed 20 people," Wilson said. "But over time you realize that if they support you ... maybe it'll make them feel that much safer at home." He acknowledges that brutal acts of war linger in the mind. "Some people, before they're about to kill someone, they think that — 'Hey, I'm about to kill someone.' That thought doesn't occur to me. It may sound cold, but they're just a target. Afterward, it's real. You think, 'Hey, I just killed someone,'" says Wilson. Insurgents "have killed good Marines I've served with. That's how I sleep at night," he says. "Though I've killed over 20 people, how many lives would those 20 people have taken?" Wilson plans to leave the Marines after his contract expires next year, and is thinking of joining a SWAT Team in Florida — possibly as a sniper.