At around 6pm on Saturday 14 July, a man in a motorcycle helmet is believed to have fired several shots at the Gatehouse pub before leaving the area in a car.
According to police, there were additional reports of men with machetes at the scene.
The pub immediately locked staff and customers inside the pub for their safety until police arrived.
Two people later presented themselves at hospital, though the injuries they sustained are not believed to be life-changing nor life-threatening according to police.
Chief inspector Jack Hadley said: “This must have been a terrifying experience for customers at the pub and I would like to reassure them that we will leave no stone unturned in our hunt for the gunman.
“Early indications are that it is gang related and not a random attack.
“I would ask that anyone who witnessed what happened and has not yet spoken to police, contact us on 101.
“Equally, if anyone captured anything on their mobile phone, please share the footage with us to assist with our investigation.”
Officers are currently speaking to witnesses at the scene and the hospital as well as viewing CCTV from the pub.
A spokesperson for the Gatehouse, which is owned by pub and restaurant operator Hungry Horse, said: "We’re working with police to support their investigation into an incident in our pub garden this evening.
"We’re supporting all our staff who are currently at the pub with police. The pub is currently closed."
Information can be given anonymously to Crimestoppers on 0800 555 111.