AMERICAN FORK — A 23-year-old Utah soldier was killed Tuesday while on a combat mission in Iraq.

Sgt. Nathan Barnes was shot as he prepared to exit a landing helicopter in south Baghdad at about 1 p.m., said his father, Kevin Barnes. Nathan Barnes served in the 10th Mountain Division, a light infantry unit based at Fort Drum, N.Y.

Four hundred American flags lined the streets leading to the Barnes home in American Fork, where Nathan Barnes was born and raised. On the house, a banner, adorned with cheerful yellow stars, read: "Sgt. Nathan Barnes: Returning home with honor."

It is the same welcome home friends and family had hoped to give the soldier at the end of this year, when they anticipated embracing the sergeant. He was deployed in August 2006 and, after a 90-day extension, his family expected him home around Christmas.

"This is so backwards," said Lisa Blake, 26, the soldier's sister. "We were going to give him a big hero's welcome — but it wasn't supposed to be like this."

Nathan Barnes enlisted at 19 because "he wanted to do it," his father said.

"We're sure he volunteered to go on the mission," Kevin Barnes said. "He was always volunteering. He told us, 'I don't like to sit around."'

And the soldier, who loved hiking, camping and hunting, didn't do a whole lot of sitting around. Blake said Nathan Barnes, who ran cross country at American Fork High School, was always complaining that he didn't get to run enough in the Army.

The soldier enjoyed a close relationship with his siblings and e-mailed and wrote his family several times a week. Just an hour before he was killed, Nathan Barnes wrote a cheery e-mail to his sister alluding to a letter, fat with stories, he had just dropped in the mail.

She discovered the e-mail shortly after she heard of her brother's death.

"I think it won't really set in that he's gone until I don't see his name in my inbox," she said.

The two often talked philosophy and discussed novels in their e-mails, Blake said.

"He'd always ask me these deep questions, and I would have to think and think to come up with good answers," she said. "He's the smartest person I know — a ravenous reader."

Family members said they would most remember Nathan Barnes for his love of children. He was looking forward to being a "present uncle," Blake said, and often talked about how much he missed his 11 nieces and nephews.