FLAGSTAFF, Ariz.—An autopsy has confirmed that a 13-year-old girl was killed by a pack of dogs while taking a walk near her family’s home on the Navajo Nation. Lyssa Rose Upshaw had extensive injuries that were consistent with canine teeth marks, including cuts and abrasions on her neck and head and deep soft tissue wounds on her legs. Her clothes were torn, and she was covered in dirt, according to the autopsy released this week in response to public records request from The Associated Press. While her mother, Marissa Jones, suspected dogs since she saw her daughter curled up off a dirt trail in Fort Defiance in mid-May, she had been awaiting an official cause. “I never thought that would ever happen to my daughter,” she said. “She was a dog lover.” The medical examiner’s office in Coconino County classified Upshaw’s death as accidental. The deadly attack has renewed discussion …