Isn't this called a deck gun volley gun? They're for dealing with mutinees, the concept was that four people could die at random and nobody wanted to be that guy so they should stand down.
A few hand-held volley guns were also developed during the 18th and 19th centuries. One of the most distinctive was the "duck's foot" volley gun, a pistol with multiple barrels arranged in a splayed pattern, so that the firer could spray a sizable area with a single shot.[7] The principle behind this type of pistol is one of confrontation by one person against a group; hence, it was popular among bank guards, prison wardens and sea captains in the early 19th century.