The man in the cowboy hat in this photo's name is Carlos Arredondo. Carlos was at the Boston Marathon with his wife handing out American flags to runners. He lost a son to a sniper bullet in Iraq in 2004 and a second son to suicide a few years later - a depression triggered by the death of his brother. Carlos now spends a significant amount of his time on peace activism and working with vets coming home from war and was at the Marathon to hand out flags and inspire people.
Carlos does not having any medical training but when the blast went off, he ran towards the danger, jumped two fences and found the now-famous man in the wheelchair on the ground, both his legs blown off, and suffering from severe shock and critical wounds. He got him into a wheelchair and pinched the man's artery closed with two of his fingers (you can see him doing so in the photo). Because of Carlos, this man is alive today, having had surgery earlier today to remove both of his legs.
This man who lost so much still threw himself into the frenzy of panic and saved another guy's life. That's Trill.
