RNA - The Limestone County sheriff's office told media on Tuesday that the shooting had occurred overnight in the town of Elkmont.
The office said five people — his father, stepmother and three siblings — had been shot, with three dying at the scene and two later in hospital.
"The 14-year-old caller was interviewed and confessed to shooting all five members of his family in the residence," it said on Twitter.
Investigators found the handgun allegedly used in the killings on "the side of the road nearby where it had been tossed," the sheriff's office said in another tweet.
Police stated that the pistol, used in the assault, had illegally been held at the residence.
Detailing the incident at a press conference on Tuesday afternoon, Limestone County sheriff's spokesman Stephen Young said, “The offender called 911 at approximately 11pm Monday evening. He met deputies in the driveway and told them that he had been in the basement of the home and heard gunshots from the main level of the home upstairs.”
Young said several discrepancies were found in the teenager’s statements, adding that, “Upon being confronted with some of the inconsistencies he did admit to shooting the five family members.”
The teenager, who has not been named in reports, is being held in a juvenile detention center and is charged with five counts of juvenile murder.
According to Press TV, Young said the investigators are still working to understand the teenager’s motive and that he could face charges as an adult.
The horrific slayings come in the wake of mass shootings in the US, including a weekend one in Texas that left seven people dead and 22 wounded, including a toddler.
Last month, a gunman killed 22 people and wounded another 24 in El Paso, Texas, while another assailant killed nine and injured 27 in Dayton, Ohio.
Experts believe President Donald Trump's controversial remarks and anti-immigrant policies have fueled hatred and increased violence in the US society.
In the meantime, leading Democrats have called for stricter gun laws, introducing legislation that would expand background checks on gun purchases, in an effort to curb the gun violence across the US.