ATHENS, Ohio -- A Hocking County gun shop owner may have prevented a mass shooting at Ohio University in Athens, authorities said.

John Downs, owner of a Logan gun shop, refused to sell a gun to 25-year-old James Howard. Howard passed a background check, but he made statements that indicated he may want to harm himself or others, according to ABC 6.

"There was a red flag for me," Downs told ABC 6. "I won't allow that; I don't want that to be on me."

Howard left the store angry after Downs refused to sell him a long gun. When Howard returned to the store more than an hour later, Downs hid his customers in a backroom, locked the store, and called 911.

Police later arrested Howard at a nearby Walmart. He was buying camouflage clothing, gloves, and ammunition.

Police found a .22-caliber rifle and mental health paperwork inside Howard's car. Authorities said Howard had purchased another weapon at an Athens gun store.

"Apparently he was frustrated about something that happened at OU in Athens," Hocking County Sheriff Lanny North told ABC 6. "I believe [Downs] did prevent a mass shooting that was probably going to occur at Ohio University in Athens."

North and Downs could not be reached for comment Sunday morning.

Howard is a former Ohio University student and hockey player.

OU Police Chief Andrew Powers told ABC 6 Howard had withdrawn from OU on Monday, the same day he tried to buy the gun. He later shoved an assistant hockey coach.

Police said Howard had been living in Athens, but had recently returned to Canfield, near Youngstown, where he had left his cell phone. Investigators had pinged the phone hoping to find his whereabouts. Detectives told ABC 6 they believe Howard was trying to throw off police so they would not know where he was after a planned attack.

A Hocking County grand jury is considering the case, according to court records.

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