Carlos Arredondo, Peace Activist At Boston Marathon Who Lost Son In Iraq, Appears To Pinch Shut Victim's Artery (GRAPHIC PHOTO)

Carlos Arredondo came to the Boston Marathon to honor his son who was killed in Iraq. But after the explosions, the mourning father channeled his grief into heroism when he tended to wounds that resembled the ones that claimed his boy’s life.

Arredondo sat perched in the bleachers on Monday, American flags in hand, near the finish line with his wife to greet the National Guard runners and a suicide support group, organizations that honor his two dead sons, ABC reports.

Lance Cpl. Alexander S. Arredondo died in Iraq in 2004 in a firefight in Najaf and his other son, Brian, who battled years of depression after his brother died, committed suicide in 2011.

But once the mourning father, turned peace activist, saw the bloody carnage, he immediately ripped away the snow fence and scaffolding that separated him from the struggling victims and started helping the critically injured, the Portland Press Herald reports.

"My first reaction was to run toward the people," he told ABC. "There was so much commotion and a lot of people running away. I was one of the first to help people and God protected me. It was horrific."

In one stunning photo that’s become an iconic image of the incredible heroism that emerged, Arredondo appears to be pinching closed a severed artery from the thigh of a victim who lost both of his legs, according to NBC. He also used his clothes and towels to help keep the victims from bleeding out.

"I kept talking to him. I kept saying, 'Stay with me, stay with me,' " Arredondo told the Portland Press Herald.

Since his son was killed in Iraq, Arredondo has changed courses completely. He quit his full-time job and now believes his purpose is to honor the fallen and protest the war, according to The New York Times.

In the years following his 24-year-old son’s death in Iraq, Arredondo paraded a mobile memorial around, complete with a coffin filled with photos of Alexander and some of his favorite possessions.

“As long as there are Marines fighting and dying in Iraq,” he told The New York Times in 2007, “I’m going to share my mourning with the American people.”