Police were alerted after a man arrived at hospital on Thursday, October 15 with injuries to his lower leg.
The injuries are suspected to have been caused by a firearm but were not considered life-threatening.
The man has since been discharged from hospital.
Another man was subsequently arrested in connection with the incident and remains in police custody while inquiries continue.
There was a visible police presence in the Maugersbury area following the incident as officers investigated the circumstances surrounding the injury.
The police scene has since been lifted, although Gloucestershire Constabulary said enquiries remain ongoing to establish how the man came to be injured and whether anyone else was involved.
The incident happened on the same day as the Stow Horse Fair, which was taking place at Maugersbury Field on Thursday, October 15.
Ahead of the fair, Gloucestershire police announced additional patrols in the area to reassure those attending and local residents.
Police also said notices had been placed around Maugersbury Field as part of a multi-agency approach to the event, stressing that these were not the result of any intelligence received.
The fair is one of Britain’s oldest traditional horse fairs and attracts members of Romany Gypsy and Traveller communities from across the UK.
Its origins have been traced to a royal charter granted by King Edward III in 1330, while a later charter from Edward IV in 1476 established its twice-yearly tradition.
Originally a medieval hiring and livestock market, it developed into a gathering centred on horse trading.
Gloucestershire police are appealing for anyone with information about the suspected firearm incident to call 101 quoting reference 53260089460.
