A 15-year-old has been arrested after Yonkers police say he opened fire on a group of people Sunday night, killing a 20-year-old man and wounding four teenagers in what investigators believe was a targeted, gang-related shooting. According to the Yonkers Police Department, the shooting happened just before 8:45 p.m. near the intersection of Elm Street and Palisade Avenue. Investigators say the suspect approached a group gathered on a street corner, stepped into the roadway, and began firing. Investigators believe he was the only shooter involved. Yonkers Mayor Mike Spano, in a press conference Monday, called for calm in the wake of the shooting and urged against any retaliatory violence.