At 10.22pm on Friday January 14 police were called to The Shoulder of Mutton pub, in Carr House Road, Shelf to reports of on altercation.
West Yorkshire Police have said the altercation involved a number of men inside the premises followed by a further incident outside a short time later.
One of the men was seen brandishing a firearm before leaving the scene in a car.
Detectives from Calderdale District CID are currently carrying out extensive enquiries to identify and arrest those involved.
Anyone with any information that could assist the investigation is asked to contact officers via 101 quoting crime reference 13220023867 or online via www.westyorkshire.police.uk/101livechat
Information can be given anonymously to the independent charity Crimestoppers on 0800 555 111.
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