(CNN) -- A 14-year-old confessed to shooting five members of his family in their Elkmont, Alabama, home, authorities said.
The victims were the boy's father, stepmother and siblings, sheriff's office spokesman Stephen Young told CNN. Investigators have yet to establish a motive, he said.
Investigators found the handgun allegedly used in the killings on "the side of the road nearby where it had been tossed," the Limestone County Sheriff's Office said in a tweet.
Earlier, the office said the teen was assisting police in locating a 9 mm handgun that he had discarded near the scene.
The shooting happened about 10:30 p.m. Monday, according to CNN affiliate WAFF. The accused teen called 911 around that time to report that he was in the basement when he heard gunfire upstairs, WAFF and fellow affiliate WHNT reported.
He repeated the claim to deputies who arrived on the scene, Young told CNN.
By 3 a.m., however, the sheriff was informing investigators that the 14-year-old had confessed to the shootings, WAFF said.
The sheriff's office first reported early Tuesday that three of the five victims were confirmed dead at the scene and two were airlifted in critical condition. The office later confirmed the airlifted victims had died as well.
The boy is being held in an unspecified juvenile facility, Young said. It's unclear if he will be charged as an adult.
A Limestone County School District spokeswoman confirmed the teen attended Elkmont High School, but referred additional questions to law enforcement.
"Limestone County Schools is deeply saddened by the tragic event," Karen Tucker said in an email. "We are concentrating our efforts in assisting our students, faculty and community in dealing with this tragedy. Additional school counselors and Limestone County Health Department Counselors are on site. These individuals will be available for as long as there is a need."
The shootings unfolded in a modest, one-story home on a large lot set back from a residential street. Elkmont, a town of fewer than 500 residents just south of the Tennessee border, is about a 45-minute drive northwest of Huntsville, Alabama.