BRENTWOOD - Police are searching for the gunman who shot and killed a teenager near his Brentwood home last night.Police say 18-year-old Juan Rosario was gunned down in a driveway along Grand Boulevard at around 10:30 p.m. Neighbor Numael Amador says he heard three gunshots. While local residents say Brentwood is a quiet community that is not known for violence, over the past two years several teens were gunned down on the streets of the town, including 13-year-old Wilson Baptista, Jr., who was shot in the head in 2009 while playing basketball.Police have not disclosed information about the circumstances of last night's shooting or any possible motives. Anyone with information is asked to call the Suffolk Crime Stoppers at 1-800-222-TIPS.