Two men were injured and a policeman was knocked to the ground during a disturbance in a bar.
Police were called to the Albany Palace pub in Trowbridge following reports of a “large fight involving several people”, early on Sunday.
Wiltshire Police have said it was studying CCTV try to find out what happened.
Tommy Arkle was in the bar at the time and filmed what happened. He described it as “unreal”.
“You wouldn’t expect such an event in a little town… its mad,” he said.
A spokesman for JD Wetherspoon said it “completely condemned the action of a large number of people in its pub. which was “distressing” to staff and customers.
“The pub has never encountered an incident like this and we will work with the police to ensure that those involved are brought to justice.”
Police are urging anyone with information to come forward as soon as possible.