Levi Aron allegedly drugged 8-year-old Leiby Kletzky before smothering him to death, the Brooklyn medical examiner said Wednesday. Aron, 35, has been charged with first-degree murder in the death of Leiby, who was found on July 13 dismembered in a Dumpster behind Aron’s apartment. The medical examiner’s office said Leiby had been given a muscle relaxant, painkillers, Tylenol, and an anti-psychotic drug normally used to treat schizophrenia. There was no sign of sexual abuse. Investigators believe Aron drugged the boy before going to work, then saw a missing-person report and panicked.