Zachary Davis: Dr. Phil interviews Tennessee 'sledgehammer killer'

Zachary Davis was just 15 when he brutally killed his mum

Zachary Davis, 15, bludgeoned his mum to death with a sledgehammer as she slept, then set the family home on fire in a bid to destroy the evidence - and kill his brother. He is one of the most unforgettable guests that has ever appeared on Dr. Phil.