The Navy SEAL who said he killed Osama Bin Laden described the moment he pulled the trigger and shot the world's most wanted man in the head.

Robert O'Neill, 41, a decorated veteran who fought in more than 400 separate combat missions, recounted his distinguished career in his new memoir The Operator.

The new book details the historic night in 2011 he stormed the high-security compound in Abbottobad, Pakistan.

As signs began to suggest the leader of al-Qaeda was indeed inside, O'Neill reminded himself to savor the moment knowing it was likely he wouldn't make it out alive.

Special forces breached the compound and a point man killed Bin Laden's last line of defense with the help of one well-rehearsed phrase before O'Neill came face-to-face with Bin Laden, who was shielded by his youngest wife in a dark room.

Robert O'Neill describes the moment he pulled the trigger and shot Osama Bin Laden in a high-security compound in Abbottobad, Pakistan

O'Neill recognized they were on to something when a breacher blew out the metal gate to the compound, only to find a solid brick wall on the other side.

While the breacher lamented their initial failure to gain entry, O'Neill said: 'No, this is good. That's a fake door. That means he's in there.'

When they finally walked into the compound, it began to dawn on O'Neill that the hunt for Bin Laden - which took nearly a decade - was coming to a head.

He thought: ' Holy s***, we’re here, that’s Bin Laden’s house. This is so cool. We’re probably not going to live, but this is historic and I’m going to savor this.'

The soldiers moved past rooms filled with women and children and made their way up a set of stairs after breaching another door.

O'Neill wrote: 'The woman intel analyst had told us we should expect Khalid bin Laden, Osama’s 23-year-old son, to be there, armed and ready, his father’s last line of defense.

'"If you find Khalid," she told us, "Osama’s on the next floor."'

A man emerged on a landing above the special forces with an AK-47, before darting behind a banister.

Robert O'Neill, a decorated veteran who fought in more than 400 separate combat missions, recounted his distinguished career in his new memoir The Operator

The point man, who learned to say 'Khalid, come here' in both Arabic and Urdu, quietly whispered the phrase - confusing the 23-year-old, who at that point was unsure American soldiers were inside the compound.

Bin Laden's son reflexively stuck his head out and said, 'What?' before he was shot in the head.

The team quickly moved up the stairs to clear more rooms, while O'Neill and the point man decided to face the architect behind the 9/11 attacks.

O'Neill wrote: 'Our tactics said we should wait for more guys, but we needed to get up there....

'And then I had a thought so clear it was like a voice in my head. I’m tired of worrying about it, let’s just get it over. It wasn’t bravery, it was more like fatigue – I’m f***ing done with waiting for it to happen.

'I squeezed his shoulder.'

When they came across two women at the top of the stairs, the point man heroically threw himself at them, thinking they were armed with suicide vests.

'If they blew up, his body would absorb most of the blast and I’d have a better chance of surviving and doing what we had come there to do,' O'Neill wrote.

When he turned to another room, he saw Bin Laden, 'taller and thinner than I'd expected, his beard shorter and hair whiter'.

A woman stood in front of him, but O'Neill didn't hesitate. He aimed above her shoulder and pulled the trigger twice, writing: 'Bin Laden’s head split open and he dropped.

'I put another bullet in his head. Insurance.'

O'Neill was part of SEAL Team Six, which conducted the May 2, 2011 raid on Bin Laden's compound in Pakistan

O'Neill was also on the missions that helped rescue Capt. Richard Phillips from Somali pirates and SEAL Marcus Luttrell from Afghanistan.

In a statement issued through publisher Scribner, O'Neill said he wanted to show 'the human side' of the battles fought for the country worldwide.

'They are extraordinary people, but they are also normal and I was proud to serve with them,' he said. 'I also wanted to show that it is possible to do anything you want, no matter where you are from, as long as you work hard, avoid negativity and never quit.'

O'Neill first alleged that he had killed bin Laden in 2014, an announcement that the government has neither affirmed nor disputed.

Around the same time, the head of Naval Special Warfare Command issued a letter criticizing violations of the SEAL 'ethos' against self-promotion.

'A critical tenant of our ethos is "I do not advertise the nature of my work, nor seek recognition for my actions,"' wrote Rear Adm. Brian Losey. 'Our ethos is a life-long commitment and obligation, both in and out of the service. Violators of our ethos are neither teammates in good standing, nor teammates who represent Naval Special Warfare.'

Another SEAL on the bin Laden mission, Matthew Bissonnette, wrote the best-selling 'No Easy Day' in 2012.

Completed under the pseudonym 'Mark Owen,' the book offered a detailed accounting of the raid but did not identify by name the SEAL who killed bin Laden.

O'Neill has been a supporter of President Donald Trump (pictured together in an Instagram post)

In his personal life, O'Neill is engaged to New York-based Jessica Halpin, age 27 (the couple pictured left and right)

Bissonnette was threatened with prison for not clearing his manuscript with the Pentagon and last year agreed to pay the government millions of dollars for back earnings and legal fees. A Scribner spokesman said the Pentagon has cleared O'Neill's book.

O'Neill is the recipient of numerous honors, including two Silver Stars, four Bronze Stars with Valor and a Joint Service Commendation Medal with Valor.

His book, Scribner announced, 'will offer powerful stories about - and new insights into - our war against terror, and will capture the fierce and unique brotherhood among SEALs - many of whom spend up to 300 days away from their families and rely on team members for their survival'.