A 14-year-old boy shot and killed all five members of his family in the US state of Alabama and then called police and confessed to the crime, local law enforcement said Tuesday.

Three of the victims were found dead at the scene, a house in Elkmont, Alabama, and the other two died later after being airlifted to a regional hospital.

"The 14-year old caller was interviewed and confessed to shooting all five members of his family in the residence," Limestone County sheriff said on Twitter.

"He is currently assisting investigators in locating the weapon, a 9mm handgun that he said he tossed nearby," it said.

The shootings occurred late Monday.

The boy in custody was not identified, and there was no immediate word on a possible motive for the murders.

Gun violence is a prevalent feature in American life with more than 36,000 deaths a year - about a third of them homicides - according to statistics compiled by the Giffords Law Center, an advocacy group.