i went like this. i did the cross, and i just went with -- i just said, god, protect me and i went on there. >> with that invocation, carlos began to move the barriers across the sidewalk and went to help the victims. it was pure instinct. years earlier in costa rica, he had been a volunteer firefighter. >> so i learned to be real quick. it helped me that day for me to realize that people was in trouble and i was there to help. >> the carnage reminded him of what his son, alex, had faced in iraq. >> i know about the ieds, and that was sort of happening right there on the sidewalk. it was like a war zone. >> including the threat of a third bomb. >> that's his nature. >> carlos's wife, melita, saw him disappear into the crowd. she was worried but not surprised.