The 14-year-old student who murdered four of his classmates in the US state of Georgia was questioned by police last year about online threats, the Federal Bureau of Investigation (FBI) said.

In May 2023, Colt Gray was questioned by police. They suspected that he was behind internet posts with images of weapons, warning of a school shooting.

The FBI said its National Threat Operations Center alerted local law enforcement after receiving tips about “online threats to commit a school shooting at an unknown location and time.”

After the location of the threats was determined, police questioned the teenager and his father.

The teenager denied sending the threats, but his father told police he had hunting rifles in the house but that the then-13-year-old “did not have unsupervised access to them.”

“At that time, there was no probable cause for an arrest or to take additional law enforcement action at the local, state, or federal level,” the FBI said in a statement.

On Wednesday, the boy opened fire with an assault rifle at Apalachee High School, killing two teachers and two students, investigators said.

Eight other students and a teacher were injured in the attack. Gray was arrested on school grounds and will be tried as an adult.

The school sent a message to parents stating that the school is “currently in a strict lockdown following reports of gunfire.”

Survivors recounted the moment Gray began attacking students. One student told the BBC she saw him leave a classroom after a math lesson and return with a gun in his hand. One of her classmates saw the gun and refused to open the door for Gray, even as he continued to bang on it.

Gray then walked into the next classroom and opened fire.

According to the BBC, this was the 23rd school shooting in the US in 2024. So far this year, 11 people have been killed and 38 injured in such attacks.