NEW YORK (AP) -- A teenager died in a hail of 20 bullets fired by police officers who thought he was holding a gun, authorities said Tuesday. The object turned out to be a hairbrush. A 911 operator heard the teen yelling that he had a gun, police said. But the case nonetheless evoked painful memories of previous police shootings: the November 2006, 50-bullet barrage that killed the unarmed Sean Bell on his wedding day, and the 1999 killing of unarmed African immigrant Amadou Diallo, who was hit by 19 of the 41 shots fired by police in the Bronx. "The circumstances of how it occurred at this point is under investigation and you can rest assured that we will take this very seriously," said Mayor Michael Bloomberg. Officers received the 911 call from the teen's mother around 7 p.m. Monday, police spokesman Paul Browne said. The 911 operator could hear the teen yelling in the background, claiming he had a gun, Browne said. When officers arrived at the Brooklyn apartment...