While the dispute was going on, some shepherds came up, bringing with them a man whose hands were bound behind his back.
Source: New York State Testing Program: ELA Common Core Sample Questions
Is bringing an adjectival participle phrase that modifies shepherds? If not, what does it modify, or what is it anyway?
Edit: Related: Parts of Speech of: come+ verbing
The participle phrase headed by bringing can be understood to modify the previous clause some shepherds came up. We need not think that it must attach to a single word in that clause, whether that be shepherds or the verb-phrase came up. The participle phrase expresses an action collateral with or incidental to the action expressed in the clause it modifies or pertains to.
Here, the primary action is {some shepherds came up} and the collateral action is {bringing with them a man who ...his back}
