How 2 surgeons and a bomb expert saved a soldier's life after a grenade tore through his torso

— -- It was a sunny spring day in eastern Afghanistan on March 16, 2006, when U.S. army soldiers in the Alpha Company headed out on patrol into the heart of Taliban country.

Capt. Billy Mariani, Private Channing Moss and Staff Sgt. Eric Wynn were part of a convoy on the move, with Moss manning a gun in the vehicle. Also on the Humvee with them was an army medic named Jared Angell, whom the men called simply, “Doc.”

Watch the full story on "20/20: The Good Doctors: Brilliance and Bravery," Wednesday, Sept. 13 at 10 p.m. on ABC.

As the convoy entered a narrow stream bed, surrounded by higher ground, Wynn said suddenly there was a “pop.”

“We’re under attack,” Moss said. “We just got ambushed.”

The men got into position as bullets cut through the air; the bullets then became rocket-propelled grenades. The men said these RPGs were the size of baseball bats with high explosives on one end and tailfins on the other, traveling at incredibly high speeds.

“I saw the first rocket hit a truck in front of me,” Moss said. “[There was] a trail of smoke and fire, and you could hear [the RPGs] just barreling through the air, then you hear the BOOM.”

The convoy was in trouble, and the men quickly realized they need to escape immediately.

“Right when I said, ‘get out,’ is when we got hit,” Wynn said. “I didn’t even finish my sentence.”

Three RPGs had hit their Humvee. Wynn said the impact felt like “one big blow.”

One of the RPGs punched through the windshield. Wynn and Moss tried to fire back at the enemy, but they both took hits. Wynn said his face was hit with shrapnel, but Moss’ situation was more serious.

“I thought I got slammed up against the truck and I went to return fire again,” Moss said. “Then I smelled something smoking and I looked down and I was smoking … I was screaming.”

“Moss … he has a tailfin sticking out of his side,” Wynn added.

Moss had been impaled with a 3-foot rocket designed to explode on impact, killing anyone within 30 feet. Except this RPG didn’t explode when it embedded itself in Moss’ torso.

“I looked at [Angell] straight in his yes,” Moss said. “I was like, ‘Doc, I don’t want to die like this.’”

Angell sprang into action and started making calls for help.

“I said [to Moss], ‘You keep fighting with me and I’ll keep fighting with you,’” Angell said.

A helicopter at a nearby medevac base was alerted, except Mariani said they left out one key piece of information.

“We didn’t tell him that Moss had live ordnance in him because there was that possibility that they might not want to transport him,” Mariani said.

Moss said he thought he was going to die, but then he heard the sound of the rescue helicopter above him. When the transport crew got to Moss, they were shocked to see the tailfin in his abdomen. Army policy states that the crew is not supposed to transport a patient in Moss’ condition because he was a human bomb, but the crew knew that if they left him, he would most certainly die.

“He was possibly bleeding to death internally, he was in shock,” said Sgt. John Collier, a flight medic and member of the transport crew. “We had to get out of that situation and get to a hospital, where they could do surgery on him.”

They decided to take Moss anyway, and very gently they loaded him on to the chopper, airlifting him to the Frontline Army Field Hospital, a rudimentary facility with limited medical resources.

When Moss was taken inside, surgeons Major Kevin Kirk and Major John Oh were joined by explosive expert Sgt. Dan Brown. The men worked side-by-side to save Moss’ life.

“I was like, ‘Is he still alive,’ and the doctor is like, ‘Yeah,’” Brown said.

They decided to X-ray Moss – by this point, the RPG had been inside of him for more than an hour – and the two surgeons and Brown were relieved to see that the deadliest part of the RPG, the explosive charge, was not in him.

“I was like, ‘OK, here, this is a good thing.’ I said, ‘The warhead’s not there,’” Brown said. “They’re like, ‘Good.’ I said, ‘Well, not all the way.’”

What was in Moss' body was the primer, a smaller explosive used to detonate the grenade. If it went off, it would kill Moss and anyone near him.

“I said, ‘It means, we don’t die, we’ll just lose our hands,’” Brown said. “And they kind of looked at me and they said, ‘You know we’re surgeons, right?’ I was like, ‘Yeah,’ I said, ‘I understand that.’”

The surgeons decided to go ahead with attempting to remove the explosive.

“I knew that if we didn’t just get this thing out, he was going to die,” Oh said. “Whether it took fingers off or not, we had to get this thing out.”

Through an incredibly delicate surgery, and knowing they were in uncharted territory, the doctors reached inside Moss and steadied the still-lethal explosive that had lodged itself inches from Moss’ heart.

Using a hacksaw, Brown gently sawed off the tailfin and eased the rocket out. The detonator was aimed at his own body.

“His theory was that if it had detonated, then it would have detonated into his flak vest,” Oh said.

Kirk said once Brown got the explosive into his hands, “he walked out at a smart pace.”

Once outside the medical facility, Brown took the rocket to a bunker and detonated it. Moss’ life was saved.

“It was the loudest sound in my whole life,” Oh said. “And just relief, and Private Moss is alive because of that.”

“He was an American, he was soldier, he was a brother, and he was one of us,” Brown said. “There was nothing going to stop us from doing what we knew he had to do.”

Watch the full story on "20/20: The Good Doctors: Brilliance and Bravery," Wednesday, Sept. 13 at 10 p.m. on ABC.