"He was all beers and bullets," recalled his wife, Masako.
But a foot injury suffered during a paratrooper training jump in 2001 compelled Sims to take a different path in the Army from the one he had planned. Instead, he studied to become a respiratory therapist, and from there became a physician's assistant.
"From the line, for the line," he was fond of saying about his transition from fighting man to a doctor's aide.
Sims was on his second tour of duty in Iraq in that capacity when he died June 16 in Mosul, north of Baghdad. Army officials said his death did not occur during combat and that the cause remains under investigation.
Masako Sims said she has been told that there were no obvious signs of trauma to her husband's body and that homicide and suicide have been ruled out. Army public affairs officers did not return e-mails seeking comment about the investigation.
He was due to wrap up his tour and return home to his wife and three young children in Arizona about two weeks after he died.
Masako Sims said she knows her husband was looking forward to taking the kids, who range from 21 months to 4 years old, for walks or to a park or museum.
"He was a great father. He was very involved," she said. "They were just the light of his life."
Masako Sims said she met her future husband later that year during freshman orientation at Howard University in Washington, D.C. They dated a little during college, but the romance didn't get serious until years later when she moved to Denver for a job with a telecommunications company and he joined the Army and was stationed in Georgia.
"We hadn't talked for about 18 months, and he tracked me down at work one day," she recalled in a recent interview.
They began a telephone relationship that grew so intense that she drove down to Ft. Benning, Ga., to see him for what was supposed to be a short visit. They were married eight days after she arrived.
In addition to spending time with his children, Masako Sims said her husband enjoyed computers, road trips, riding his bike and puttering around the house. One of the things she loved most about him, she said, is that he allowed her and the kids to see behind the tough soldier facade.
"We were best friends," she said. "He was everything to me."
Masako Sims said she had put her children in the car and was getting ready to run some errands last month when she ran back into the house to grab something she'd forgotten.
As she prepared to come back outside, she saw two uniformed soldiers approaching the front door, one of them holding a Bible.
"As soon as I saw them, I knew he was dead," she said. "It was the worst day of my life."