Another View From Iraq's Deadly Checkpoint

For two years, Army Spc. Mario Lozano has agonized about taking the life of an Italian secret agent when he was manning a mounted machine gun at a U.S. roadblock one night on what was the most dangerous highway in Iraq.

"I get nightmares," Lozano told CBS News chief foreign correspondent Lara Logan in an exclusive interview. "I think about that guy, almost every day."

He says had no idea who was inside the car that came speeding towards his unit after curfew, so he flashed a warning light.

"Iraqi civilians; when they see that big spotlight — that means stop," Lozano said.

But he says the car carrying agent Nicola Calipari and the Italian hostage he had just freed kept going.

What was going through his mind at that point when he saw the car coming at him?

"My daughters," Lozano said. "I mean, my daughters (are) like No. 1 in my life. I just don't want them to grow up without a kid, you know, without a father."

So Lozano said he fired a warning shot.

"The car still didn't stop," he said. "So I just … had to shoot at the car. I had no choice."

Lozano's bullets killed Calipari and wounded journalist Giuliana Sgrena, who had just survived 28 days as a hostage. After the incident, Lozano was silenced by the military — but Sgrena told the world U.S. soldiers deliberately tried to kill her.

"So when the Italian journalist said there was no light flashed, that's not true?" Logan asked.

"It's not true," Lozano said.

"When she says there's no warning shots, is that true?" Logan asked.

"There was warning shots," Lozano said. "It's not true."

"When she says the vehicle was fired upon 3 to 400 times, is that true?" Logan asked.

"No, that's a lie," Lozano said. "Because in order for that to happen, I would have had to reload."

Those details have never been heard in Italy, where thousands poured onto the streets to mourn their national hero. His death enraged a nation already turning against an unpopular war.

Dan O'Shea, a Navy SEAL and head of Iraq's Hostage Working Group at the time, says what happened is not Lozano's fault.

"He was doing what he was trained to do, and he needs to be defended for that," O'Shea said.

He believes the Italians didn't want their U.S. ally to know they'd paid a ransom to the hostage takers, and that Calipari himself ordered the U.S. to be kept in the dark.

"He's got no one to blame for his death, unfortunately, other than himself," O'Shea said of Calipari.

But it's Mario Lozano who is being tried in absentia for murder in Italy.

"In your mind, in your conscience, are you clear of any wrongdoing?" Logan asked.

"Yes," Lozano said. "I'm just an infantry soldier, doing my job, you know."

"If you were talking to his sons and family right now, what would you say to them?" Logan asked.

"That's tough. I don't even know if I could look at them in the face, really," Lozano said. "Not because I feel like I did anything wrong; it's because I know the grief they might have gone through."

That's a burden Lozano says he will carry for the rest of his life.