Forsyth County police arrested a man Wednesday for allegedly threatening to shoot up a school in Gwinnett County.

Police later found bomb shrapnel, several rounds of bullets and improvised explosive devices at his home in Cumming.

On Tuesday, Joseph John Medved, 51, attempted to purchase a shotgun from a pawn shop but had to wait 24 hours for a background check. Later that day, he made the threat at a health treatment center in Roswell, the Fulton County Sheriff’s office said. The receptionist and several patients at the clinic notified the local police, who sought a warrant and began following Medved.

“We’re very grateful for the people at the clinic,” said Tracy Flanagan, spokeswoman for the Fulton sheriff’s office. “They heard him and knew something was wrong. We always tell people, ‘If you see something, say something.’ They’re the heroes in this matter.”

Police followed Medved to the pawnshop Wednesday, authorities said. A few hours later, police witnessed Medved firing the rifle on a road outside his home and promptly arrested him.

He was booked into the Fulton County jail on Thursday evening and is expected to appear in court Friday.