We are seeking witnesses to a disturbance involving several men in Church Road, St Leonards-on-Sea, during which gunshots were heard.
It happened shortly after 11pm on Saturday (5 October) and involved an altercation between one man and a small group of other men.
No one was hurt and immediately afterwards a dark-coloured saloon style car was seen to speed off.
The source of what sounded like shots being fired is still being investigated.
Detectives are keen to hear from anyone who saw or heard anything of what happened, or who noticed a car being driven in the area of St Leonards around 11pm, possibly at speed or in an erratic manner.
Det Insp Jon Gillings said: "This was an isolated incident and there were no reports of anyone having been hurt. We need to establish exactly what happened, and hence we'd ask any witnesses to call without delay."
Anyone able to help should contact Sussex Police online or by dialling 101, quoting Operation Barmill.
Alternatively, they can pass details anonymously to the independent charity Crimestoppers, telephone 0800 555 111.