One of the most graphic images to emerge from the Boston Marathon bombings was of a young man who appeared to have lost both his legs.
He was conscious and gripped a tourniquet above one thigh as rescuers frantically wheeled him to help.
One of those rescuers has been identified as Carlos Arrendondo, a Costa Rican immigrant whose son, a Marine, died serving in Iraq in 2004, motherjones.com has reported.
The day he learned of his son's death, Arrendondo - who is wearing a cowboy hat in photographs of the scene - locked himself in a van and set it on fire.
He survived the incident and became a peace activist, and was among those who rushed towards the carnage after yesterday's explosions.