CLARKSVILLE, Tenn. -- A soldier just home from teaching medical treatment to soldiers was forced to use what he taught on Tuesday.

Video: Soldier Aids Boy Struck By Car

Sgt. Maj. Stephen Blake was in Afghanistan last week. As part of a training exercise, he was reminding soldiers how to properly tie a tourniquet.

He said he was looking forward to a few days at home away from broken bones and bloody injuries, but early Tuesday as he drove along Purple Heart Highway in Clarksville, he came upon an accident.

A car had just struck 15-year-old Joshua Castle as he walked to school.

"I spotted something in the road and I didn't know what it was, and I had to look three times. And when I looked again, I knew it was a child," he said.

He said several people had already stopped, but no one had rushed over to help Castle.

"I tell my soldiers, 'The first person to move causes everyone else to move,'" he said.

So he and two other soldiers took action. One tried to keep the boy alert, and another helped control the blood flow to the boy's leg. Blake tied a tourniquet that doctors said saved Castle’s life.

"His leg was almost completely severed," Blake said.

Blake said he has yet to meet Castle but hopes his parents find comfort in the same words he whispered to their son on the side of the road.

"What I said was, 'The Lord had him and we were here to help him," he said.

The names of the other soldiers who helped Blake are Daniel Runyon and Daniel Mapel.

Clarksville police plan to honor all three.