Sheehan was killed on the night of 5 September 1942, when "Gregory" was sunk by gunfire from an Imperial Japanese Navy cruiser and three destroyers during the Naval Battle of Guadalcanal. A U.S. Navy pilot, mistakenly thinking "Gregory" was a Japanese submarine, dropped a string of flares over the surprised ship, silhouetting her against the blackness and allowing the Japanese to detect her. Desperately overmatched by the four Japanese ships and, despite a gallant effort by its crew, "Gregory" dead in the water within three minutes. After "Gregory"s crew had abandoned ship, the Japanese began shelling the helpless survivors in the water, killing 11, including Sheehan.