Just after 1.30pm on Wednesday (November 9) police responded to a report of a male in possession of a firearm in Elm Grove Road, Littlehampton.
This is believed to be an isolated incident and there is no threat to the wider community.
There is likely to be a visible police presence in the area while officers continue their investigation. A 17-year-old boy has been arrested on suspicion of possessing a firearm with intent to cause fear of violence, he remains in custody at this time.
Anyone with information which could help officers with their investigation is asked to report it to Sussex Police online or call 101 quoting serial number 676 of 09/11.
