He was just a teenager when he made a first kill and little did Nick Irving know he would become one of the deadliest snipers in American military history.
It was on the front line in Iraq that the then 18-year-old killed a man for the first time when he fired seven shots into his head and body.
Since then he killed 33 Taliban on a single tour of Iraq and has taken part in some of the bloodiest missions in the Middle East.
Nick, now, 30, describes some of his kills as "like playing whack-a-mole".
One of the most brutal battles Nick was involved in was dubbed the Hotel Party.
He described it as "an experience" as troops were hanging out of helicopters with all types of weaponry.
Nick admits he lost track of how many men he killed in the bloody battle.
In his book, The Reaper, he says: ""I took a moment for it to sink in. I’d just shot somebody in the head.
"Another dude popped up. Was it the first guy that I thought I’d taken out? Were there a bunch of dudes in that room?
“Didn’t matter. I needed to take them out even if they seemed like they were zombies.”
Speaking to news.com.au Nick told of the moment one of his comrades was shot in the assault and how then, worse news com.
They were out of ammunition - but that's when the pilots sprang into action, leaning out of helicopters and firing shots until they ran out of bullets.
Nick, who left the army six years ago, admits there were times what he was doing jarred.
And he recalls how the war in Iraq didn't just affect the troops on the ground and also had a profound impact on those they had been tasked with liberating.
After the conflict ended, Mosul was a broken mess of rubble, smoke and devastation.
And as troops took to the streets openly for the in daylight, Nick says he was stunned by what he saw.
He writes: "Going out into the streets of Mosul in full-on daylight was literally and figuratively eye-opening. I’d heard people say we should blow Iraqis and others into the Stone Age, and it kind of looked like we had tried.
“Shattered buildings and islands of rubble all dotted the landscape.
“All I know is that we had each other’s backs at the time and did everything we could to support one another. Whether or not the higher-ups did the same is tough to say.”
After six years in the forces, Nick was struggling with life on the front line.
He penned his first book in what he admits was a blur of booze and post-traumatic disorder brought on by what he had seen during his time in the conflict.
His first book was a huge success and he is now a regular speaker and is often seen on TV in the US.
Jay-Z is even producing an NBC miniseries based on his first book and will star Emmy award actor Sterling K Brown.
But he isn't over his experiences in Iraq.
He admits he stays away from large groups of people with firearms after the murder of American Sniper Chris Kyle.
But now he is coming to terms with life as a civilian, he wants to do all he can to help other veterans returning from war zones.
Nick said: “Special ops guys have been overseas and seen different things. In the military community, we harp on about not expressing emotions, you’re the tough guy. That eats guys up in the long run.
There’s nothing wrong with talking about what you did overseas, what not to do, what to do.
“Everyone has feelings, emotions.
“No one really prepares you ... in the military you get into a mindset of ‘failure is not an option.’ You’re not used to rejection, the army doesn’t allow it.
"On the civilian side, you get that. The first dose is hard to overcome, then you realise, ‘this is just life’.
“I’ve learnt a lot from struggle. You have to go through struggles to appreciate things.
“I miss the brotherhood and camaraderie but killing, getting shot at, you can only go so far.”
Way of the Reaper: My Greates Untold Missions and the Art of Being a Sniper is on sale now