The suicide bomber, an Iranian national named Ismail Ascari,[39][40] detonated his explosives, which were later estimated to be equivalent to approximately 9,525 kilograms (21,000 pounds) of TNT.[3][4] The force of the explosion collapsed the four-story building into rubble, crushing to death 241 American servicemen. According to Eric Hammel in his history of the U.S. Marine landing force,