Boy, 3, takes father's gun from carFather is a police officer'Accidently shoots playmate'An off-duty police officer's three-year-old son has reportedly shot and killed a three-year-old cousin with his father's gun in the US.Police were called to a house in Rayville, Louisiana at 2.30 p.m. local time yesterday, the News-Star reported.Sheriff Charles McDonald said the children - a boy and a girl - were playing out the front of the house when the off-duty officer went to get something out of his car.While he was turned, the boy walked up and picked up the officer’s firearm, which was in the driver’s side door.The boy then pulled the trigger and accidentally shot the girl, killing her instantly, Sheriff McDonald said.He described the death as a "tragic accident".