He fired just three of the 50 shots, but the department says he is just as guilty as the others in his use of deadly force.
Detective Gescard Isnora claims he opened-fire because he believed that one of Sean Bell's friends was reaching for a gun.
Officer Carey testified Thursday that he fired because Isnora was firing, "Hearing the gunshots, seeing the glass breaking," he said, "I believed there to be gunfire coming from the car and going into the car."
It was Isnora's decision to use deadly force that the other four officers used to justify their own actions. Three of the officers faced criminal charges and were acquitted.
Two of the five officers, Carey and Isnora, are on trial this week for violating departmental guidelines.
But Carey, like Isnora, was forced to admit he never actually saw a weapon or anything that looked like one.
"You never saw a muzzle-flash inside that car?" asked the department's attorney. "Correct." answered Carey.
"When I saw Det. Isnora firing and heard him saying, 'Gun!' those were the final factors in determining to fire my weapon."
Sean Bell's fianc?e says the officers don't belong on the force. The PBA president says the shooting has been scrutinized long-enough.