My 6 month old beagle staps and growls?

He has started tonight just growling when he has something he shouldn't have . When I try to rake it off him he growl and has went to bite me cos he doesn't wanna give it back . Beagle are not meant to be like this so I don't no if this is gonna get worse ! And how do I nip this on the bud now before he's an adult dog .