"Little Boy" was the codename for the atomic bomb dropped on Hiroshima on August 6, 1945 by the Boeing B-29 Superfortress Enola Gay, piloted by Colonel Paul Tibbets of the 393rd Bombardment Squadron, Heavy, of the United States Army Air Forces. It was the first atomic bomb to be used as a weapon. The bomb was dropped at approximately 08:15 (JST). After falling for 44.4 seconds, the time and barometric triggers started the firing mechanism. It was less powerful than the Fat Man, which was dropped on Nagasaki, but the damage and the number of victims at Hiroshima were much higher, as Hiroshima was on flat terrain, while the hypocenter of Nagasaki lay in a small valley. According to figures published in 1945, 66,000 people were killed as a direct result of the Hiroshima blast, and 69,000 were injured to varying degrees. Of those deaths, 20,000 were members of the Imperial Japanese Army. By the end of the year, injury and radiation brought the total number of deaths to 90,000-166,000. The population before the bombing was around 340,000 to 350,000. About 70% of the city's buildings were destroyed, and another 7% severely damaged.