An off-duty police sergeant was injured and a teen gunman was killed Thursday during exchange of gunfire in Fort Greene.

Police say Sergeant James Rector stumbled upon a 17-year-old holding a gun to a man?s head who was on his knees shouting for help. According to police, when Rector identified himself as a police officer, the teen gunman opened fire, hitting Rector twice. Mayor Bloomberg (R-NY) says Rector was able to return fire and struck the teen several times.

Rector is listed in stable condition at Belview Hospital. The teen gunman was pronounced dead at Brooklyn Hospital. The man who Rector was trying to save was also wounded in the leg and is listed in stable condition.