After Monday's blasts at the finish line of the Boston Marathon sent runners and spectators scrambling, Carlos Arrendondo, bloodied and shaken, ran in to help.
"It was a horrifying scene for everybody there," he said.
Arrendondo was at the finish line, watching with a military group, because his son had been killed in Iraq.
And this was like a war zone.
Many people lost limbs in the impact.
Others were unconscious on the sidewalk.
Arrendondo says he and first responders did what they could to treat the injured.
"We started putting pieces of clothing on people's legs, a lot of bleeding, limbs all over the sidewalk," he said. "It's very sad. Very sad."