Boston police are trying to locate a 19-year-old man missing from Roxbury. Demitrius Pepin-Cepeda, who police say lives with a developmental disability, was last seen Monday around Wheatley Way. He is described as 5-foot-10, 130 pounds, with hair styled in an afro, glasses and often wears a silver chain with an arrow-shaped charm. He may have been wearing all black clothing and walks with a distinct gait, according to police.