Carlos Arredondo, or "the man in the cowboy hat" is such an inspiration.
After surviving the loss of two sons and a suicide attempt, he became a peace activist. And now he's a hero.
When you hear him speak, he seems so hurt that he could only help one person, but to that one, Jeff Bauman and to his family, it was more than enough.
Mr Arredondo shares his story
His shirt says Tough Ruck, a team of soldiers who completed the marathon then helped at the scene.