Who is Ava Olsen in the nonfiction book, Children Under Fire?

Ava Olsen is eight years old when the book opens, and she has already gone through hell. She was a first-grader when a teenager, Jesse Osborne, started shooting at her classmates as they walked onto the Townville Elementary playground for recess. She has been diagnosed with severe post-traumatic stress disorder (PTSD) and takes a cocktail of antidepressants and anti-psychotics. She lost her very best friend in the world, fellow first-grader Jacob Hall, on the day of the shooting. At times, she feels guilty about his loss and she tries to figure out what she could have done differently to save him. Her parents do their best to convince her that the shooting was not her fault.