A 19-year-old with no criminal record started a deadly gang-related shooting at a Brooklyn lounge when he opened fire on a rival. He was later killed in the gun battle, police said Monday.
According to the NYPD, Marvin St. Louis, 19, fired the first shots at Jamel Childs, 35, a member of the Folk Nation gang. Childs shot back, and two more men also started shooting.
Both St. Louis and Childs died, along with Amadou Diallo, 27, who police said was an innocent bystander…