WASHINGTON (CNN) -- When a grenade bounced off his chest and fell to the floor near his fellow troops, Petty Officer 2nd Class Michael Monsoor acted out of instinct.
His actions didn't stem from a lack of training. His instant reaction was to protect his comrades.
The Navy says he committed a selfless act: jumping on the grenade and taking the full force of the blast.
President Bush presented Monsoor's parents with a posthumous Medal of Honor for their son at an emotional White House ceremony on Tuesday. Watch Monsoor's sister share her memories »
Bush quoted one of the SEALS saved by Monsoor as saying, "Mikey looked death in the face that day and said, 'You cannot take my brothers. I will go in their stead.'" Watch the president bestow the award »
Monsoor was one of the U.S. military's most highly trained combatants, a Navy SEAL. He's the first SEAL to receive the Medal of Honor for actions in Iraq.
On September 29, 2006, Monsoor was part of a major clearing and isolating operation to root out enemy fighters holding parts of Ramadi, the Sunni insurgent stronghold west of Baghdad.
Monsoor was in a sniper position on a rooftop along with two other SEALs when a grenade flew into his location from out of nowhere. It bounced off his chest and landed in an area where it probably would have killed or seriously wounded all three of them.
Monsoor was in a position to escape before the explosion but instead leapt on the grenade.
"He recognized immediately the threat, yelled 'grenade' and due to the fact that two other SEAL snipers, our brothers, could not possibly escape the blast, he chose to smother it with his body, absorbed the impact and lost his life in the process," said Lt. Cmdr. Seth Stone, Mansoor's platoon commander.
The blast did not kill him right away; he hung on for 30 minutes. His two comrades were wounded but survived the shrapnel that ripped through their bodies.
Stone said: "He essentially saved [the] Navy SEALS on the rooftop and three Iraqi soldiers who were there."
Until this month, when the White House announced that Monsoor would receive the Medal of Honor posthumously, few people knew of his story.
Born in 1981 in Long Beach, California, Monsoor excelled as a high school athlete. He joined the Navy before the September 11 attacks.
In 2004, Monsoor graduated from the basic SEAL training course as one of the top members of his class. By March 2005, he had completed his training and was assigned to SEAL Team 3, Delta Platoon.
In April 2006, that unit deployed to Iraq's troubled and violent western provincial capital of Ramadi. Monsoor would not return home alive.
His five-month stay in Ramadi was marked by constant attacks. As a heavy machine gunner, Monsoor had to stay behind the point man on foot patrols and protect the unit from attacks.
Delta Platoon was involved in attacks on 75 percent of its missions in a highly contested part of Ramadi called the Ma'laab district, according to the Navy.
On a patrol less than a month after arriving in Iraq, Monsoor showed some of his selfless instinct when gunfire hit a fellow SEAL in the leg.
Monsoor "ran out into the street with another SEAL, shot cover fire and dragged his comrade to safety while enemy bullets kicked up the concrete at their feet," according to Navy documents.
He received the Silver Star, the third highest award for valor in combat.
His unit continued to endure the constant barrage of attacks and some 35 firefights with insurgent forces over the scorching Iraqi summer.
Monsoor also was saddled with carrying heavy radio equipment on his back as the "SEAL communicator" who called in tank and other support during firefights.
He received the Bronze Star for his work as an adviser for Iraqi troops.
"His leadership, guidance and decisive actions during 11 different combat operations saved the lives of his teammates, other [U.S.-led] coalition forces and Iraqi army soldiers," according to Navy documents.
But it was his instinct on his last operation on that Ramadi roof that solidified Monsoor's standing as a hero. E-mail to a friend