WINDER, Ga. (AP) — Georgia police questioned a 13-year-old boy more than a year ago as they investigated online posts threatening a school shooting, but investigators didn’t have enough evidence to make an arrest. On Wednesday, that boy was opened fire at his high school Outside Atlanta, four people were killed and nine injured, officials said.

The teen has been charged as an adult with using an assault rifle to kill two students and two teachers at Apalachee High School in the hallway outside his math classroom, Georgia Bureau of Investigation Director Chris Hosey said at a news conference.

It was the last among the dozens of school shootings in the US in recent years, including the particularly deadly one in Newtown, Connecticut, Parkland, FloridaAnd Uvalde, TexasThe classroom killings have stoked heated debates about gun control and rattled the nerves of parents whose children grow up with the habit of active shooter drills in their classrooms. But little has changed in the nation’s gun laws.

When the teenager sneaked out of class on Wednesday, Lyela Sayarath thought her quiet fellow student, who had recently transferred, was skipping school again. But he returned later and wanted to go back in. Some students tried to open the locked door, but instead stepped back.

“I guess they saw something, but for some reason they didn’t open the door,” Sayarath said.

The teenager then pointed the gun at people in the hallway.

He has been charged in the deaths of students Mason Schermerhorn and Christian Angulo, both 14, and teachers Richard Aspinwall, 39, and Christina Irimie, 53, Hosey said. The teen, now 14, was scheduled to be taken to a regional juvenile detention center on Thursday.

When the teenager was not allowed to return to his classroom, Sayarath heard a barrage of gunfire.

“There were about 10 or 15 at a time, right behind each other,” she said.

The math students dropped to the ground and crawled around, looking for a safe corner to hide in.

Two school resource officers encountered the shooter within minutes of a report of shots fired, Hosey said. The teen immediately surrendered and was arrested.

At least nine other people — eight students and a teacher at the school in Winder — were taken to the hospital with injuries. All were expected to survive, Barrow County Sheriff Jud Smith said. Authorities are still investigating how the teen obtained the weapon used in the shooting and got it into a school with about 1,900 students in a rapidly suburbanizing area on the edge of the sprawling Atlanta metropolitan area.

“All those students who had to see their teachers and classmates die, those who had to walk out of school limping, they looked traumatized,” Sayarath said.

It was the 30th mass murder in the US so far this year, according to a database maintained by The Associated Press and USA Today in cooperation with Northeastern University. At least 127 people have died in the killings, which are defined as incidents in which four or more people die within a 24-hour period, not including the killer — the same definition used by the FBI.

The teen was questioned after the FBI received anonymous tips in May 2023 about online threats to commit an unspecified school shooting, the agency said in a statement.

The FBI was able to contain the threats and refer the case to the Jackson County Sheriff’s Department, which borders Barrow County.

The sheriff’s office interviewed the then-13-year-old and his father, who said there were shotguns in the house but the teen didn’t have unescorted access to them. The teen also denied making threats online.

The sheriff’s office alerted local schools to monitor the teen, but there was no probable cause for an arrest or additional action, the FBI said.

Hosey said the state Division of Family and Children Services also had prior contact with the teen and will investigate whether that is related to the shooting. Local news outlets reported that the teen’s family home in Bethlehem, Georgia, was searched Wednesday.

On Wednesday night, hundreds of people gathered at Jug Tavern Park in downtown Winder for a vigil. Volunteers passed out candles. Some knelt as a Methodist minister led the crowd in prayer after a Barrow County commissioner read a Jewish prayer of condolence.

Christopher Vasquez, 15, said he attended the vigil because he needed grounding and a safe space.

He was practicing with the band when the lockdown was announced. He said it felt like a normal practice as students lined up to hide in the band closet.

“When we heard banging on the door and the SWAT team came to take us out, I knew it was serious,” he said. “I just started shaking and crying.”

He finally calmed down once he got to the football stadium. “I just prayed that everyone I love was safe,” he said.

___

Associated Press reporters Sharon Johnson, Mike Stewart and Erik Verduzco in Winder; Beatrice Dupuy in New York; Russ Bynum in Savannah, Georgia; Charlotte Kramon, Kate Brumback and Jeff Martin in Atlanta; and Mark Thiessen in Anchorage, Alaska, contributed.