From
Wikipedia:
On December 7, 1941, shortly before 0800, Japanese aircraft from six fleet carriers struck the Pacific Fleet as it lay in port at Pearl Harbor, and — in the ensuing two attack waves — wrought devastation on the Battle Line and on air and military facilities defending Pearl Harbor.
Onboard Arizona, the ship's air raid alarm went off about 07:55, and the ship went to general quarters soon thereafter. Shortly after 08:00, a bomb dropped by a high-altitude Nakajima B5N "Kate" torpedo bomber from the Japanese carrier Kaga hit the side of the #4 turret and glanced off into the deck below, starting a small fire but causing minimal damage.
At 08:06, a bomb from a Hiryū "Kate" hit between and to port of Turrets #1 & 2. The subsequent explosion — which destroyed the forward part of Arizona — was due to the detonation of the ammunition magazine, located in an armored section under the deck. Most experts seem to agree that the bomb could hardly have pierced the armor. Instead, it seems widely accepted that the black powder magazine (used for aircraft catapults) detonated first, igniting the smokeless powder magazine (used for the ship's main armament). A 1944 BUSHIP report suggests that a hatch leading to the black powder magazine was left open, with perhaps inflammable materials stocked nearby. A US Navy historical site goes as far as to suggest that black powder might have been stockpiled outside of the armored magazine. However, it seems unlikely that a definitive answer to this question might be found. Credit for the hit was officially given to Petty Officer Noburu Kanai, who was considered to be the JNAF's "crack" bombardier; his pilot was Tadashi Kusumi. The cataclysmic explosion ripped through the forward part of the ship, touching off fierce fires that burned for two days; debris showered down on Ford Island in the vicinity. Ironically, the blast from this explosion also put out fires on the repair ship Vestal, which was moored alongside.
Acts of heroism on the part of Arizona's officers and men were many, headed by those of Lieutenant Commander Samuel G. Fuqua, the ship's damage control officer, whose coolness in attempting to quell the fires and get survivors off the ship earned him the Medal of Honor.
Posthumous awards of the Medal of Honor also went to Rear Admiral Isaac C. Kidd, the first flag officer killed in the Pacific war, and to Captain Franklin Van Valkenburgh, who reached the bridge and was attempting to defend his ship when the bomb hit on the magazines destroyed her.
The blast that destroyed Arizona and sank her at her berth alongside of Ford Island took a total of 1,177 lives of the 1,400 crewmen on board at the time - over half of the casualties suffered by the entire fleet in the attack.