A man who allegedly threatened to shoot up the Hartsfield-Jackson Atlanta International Airport was arrested after entering a terminal at the airport on Monday, according to authorities.

The man’s family alerted police that the suspect had been streaming on social media Monday morning that he was headed to the airport to “shoot it up” and was in possession of a semi-automatic assault rifle, according to Atlanta Police Chief Darin Schierbaum.

The man — identified by the Atlanta Police Department as Billy Cagle, 49, of Cartersville, Georgia — was taken into custody at the airport, police said. Officers located an AR-15 assault rifle with 27 rounds of ammunition in his pickup truck parked outside the airport, Schierbaum said.

The suspect is a felon who has mental health challenges, officials said. He has been charged with terroristic threats and criminal attempt to commit aggravated assaults, among other counts, the police chief said.

“Because of the community — in this case, the family — as well as the joint collaboration of law enforcement, a tragedy was indeed averted,” Schierbaum said at a press briefing Monday.

The police chief said Cagle arrived at the airport at 9:29 a.m. and, upon entering the south terminal, went to the TSA check-in area and was “scanning that area.” Schierbaum said he believes Cagle was walking back to his truck with the intent to retrieve the weapon when officers encountered him at 9:54 a.m. and he was taken into custody.

“I do believe he was likely to use that weapon inside the crowded terminal,” Schierbaum said.

The suspect’s family reported the alleged social media threat to Cartersville police, who immediately alerted the Atlanta Police Department at approximately 9:40 a.m., according to Schierbaum.

Cartersville Police Capt. Greg Sparacio told reporters Cagle’s family alerted Cartersville police shortly after 9:30 a.m. that the suspect was “en route to somewhere in the Atlanta area” and he “had the intention to do harm to as many people as he could.”

Investigators determined what vehicle he was traveling in and provided that information to Atlanta police, he said.

Sparacio said their department is “familiar” with Cagle and he has a criminal history, though he did not go into detail.

Atlanta Mayor Andre Dickens said he is grateful a potential tragedy was averted at the world’s busiest airport.

“We’re thankful to God and to good information and good intel and good people for this crisis being averted,” he said during the briefing.