A 12 year old boy went trick-or-treating in South Carolina, USA. He knocked on the door of a house with the porch light turned on - often taken as a sign that someone is home and ready for trick-or-treating.
A man inside, however, thought he was being robbed, and opened fire with an AK-47, an assault rifle, through the door. At least 29 rounds were fired, killing the boy.
The story can be found in the New York Times, CNN.com, and other sources.