NEW YORK — A 11-year-old boy with autism slipped out of his Brooklyn school and was missing for several hours Tuesday afternoon before being found 18 miles away, police and a local lawmaker said on social media. The student, who is nonverbal, ran out of P.S. K369 Coy L. Cox School in Downtown Brooklyn through an emergency exit after noon, according to education officials and police. The school is part of District 75, a network of public school programs serving children with complex disabilities. School safety reported the boy found on social media before 4:30 p.m. He was located in Malverne, L…