Kennedy, 34, of Devon, passed an instant background check at a Pennsylvania gun shop on March 16 and walked out with the semiautomatic rifle, the prosecutor said. Twelve days later, he took the gun to the store on Sugartown Road for what was supposed to be a child-custody exchange. Instead, he shot Stephanie Miller, 37, several times in the head and stomach at point-blank range, authorities said. She was pronounced dead at the scene.