The father of a teenage student who killed two teachers and two classmates in a Georgia high school shooting two years ago was sentenced on Thursday to 15 years in prison for providing his son with the weapon used in the attack. Georgia law defines second-degree murder as causing the death of a child by committing the crime of cruelty to children. Prosecutors said Gray gave his son the rifle as a Christmas gift along with ammunition, a gun sight and other shooting accessories. Gray, they said, had showed signs of deteriorating mental health in the weeks leading up to the shooting at the school about 45 miles east of Atlanta. But Brad Smith, the Barrow county district attorney, said Gray “was convicted for what he did know”.