Witnesses will identify Jesean M. Callender as the teenager who fatally shot a 15-year-old boy during a gang dispute near Linden-McKinley STEM Academy, a prosecutor told jurors this morning as Callender’s murder trial began in adult court. Callender, 17, fired a 9mm handgun into a crowd gathered for a fight in an alley behind 2055 Cleveland Ave., killing Kaewaun D.