The Hampden County DA won't be filing criminal charges after an investigation of the drowning death of 12-year-old boy at a Springfield school last year. Mark Mastroianni said in a report Wednesday it's unclear why or how Marlon Brown drowned Feb. 15, 2013, in the Kiley Middle School pool. He said several factors may have contributed but none support criminal charges. Mastroianni said there's no evidence anyone saw or heard Marlon call for help before he was found at the bottom of the pool near the slope from the shallow end to the deeper section. Marlon was among 45 students being supervised by two physical education teachers during a free swim period in which some students were stopped from splashing and rough play, and one student got sick just outside the pool.