Police arrested a teenager for allegedly shooting a 6-year-old boy, his mother, and three others during an unofficial Caribbean J’Ouvert celebration in Crown Heights on Labor Day Monday. A 15-year-old is facing charges for the shooting and for possession of a weapon, according to District Attorney Eric Gonzalez, who said he will charge the teen as an adult.  The teen allegedly fired a barrage of shots shortly before 3 am on Monday, shooting the six-year-old boy, his mother, and three other men in the feet and legs at the intersection of Nostrand Avenue and Crown Street, cops said.  The young boy and his mother, 47-year-old Patricia Brathwaite, were rushed to the hospital with non-life…