Police responding to a 9-1-1 call found Plowden dead on the floor of a room where he had been staying with his girlfriend, whose name is being withheld.
Police say Williams and two other men were staying in a separate room, and were acquainted with the victim. A motive for the shooting is still under investigation.
Police say they have recovered a gun believed to be the murder weapon from the motel's parking lot.
Williams was apprehended by Moorestown police in the parking lot of the next-door Bel-Air motel. The two men who were staying with Williams were also detained, but are not facing any charges.
Williams is being held on $750,000 bail.
