Only Child by Rhiannon Navin
Squeezed into a coat closet with his classmates and teacher, first grader Zach Taylor can hear gunshots ringing through the halls of his school. A gunman has entered the building, taking nineteen lives and irrevocably changing the very fabric of this close-knit community. While Zach's mother pursues a quest for justice against the shooter's parents, holding them responsible for their son's actions, Zach retreats into his super-secret hideout and loses himself in a world of books and art. Armed with his newfound understanding, and with the optimism and stubbornness only a child could have, Zach sets out on a ... journey towards healing and forgiveness, determined to help the adults in his life rediscover the universal truths of love and compassion needed to pull them through their darkest hours.