This doesn't actually specify shot only once in the head, does it? It only says shot in the forehead, leaving unsaid how many times shot. Reporters these days do not seem concerned with specifics or accuracy in their reporting. Most reporting these days is about reporting the emotional reactions to what happened, not reporting details of what happened.

His mother, Nancy Lanza, was found shot through her forehead by a .22-caliber rifle left in her second-floor bedroom. Nearby was a blue-and-white duffel bag containing 50 rounds of rifle ammo, ear protection, eye protection, binoculars, paper targets and a certificate from the National Rifle Association bearing Adam Lanza's name.
[link to www.cnn.com]