The boy exchanged the handgun for $300 in February. The incident was discovered after ammunition was found in the backpack of the other student Wednesday.

Two 10-year-old students were arrested in connection with a gun sold at their elementary school in Florida, county officials confirmed.

A deputy’s son “agreed to exchange a handgun, (later found to belong to his deceased father), for a sum of $300” back in February, the Hendry County Sheriff’s Office said in a statement.

The Country Oaks Elementary School was placed under lockdown Wednesday morning after the sheriff’s office received a call about “a suspicious incident” on campus. Authorities discovered ammunition in the backpack of the boy who purchased the gun.

The gun was later found in his backyard under a shed, hidden with a 74-gram bag of marijuana, according to investigators.