LAS VEGAS—Police learned Saturday that New Orleans Saints running back Alvin Kamara was a suspect in a pre-dawn beating of a man at a Las Vegas nightclub, but did not arrest Kamara until after Sunday’s NFL Pro Bowl, a Las Vegas Metropolitan Police Department spokesman acknowledged Monday. The alleged victim in the attack was treated for facial injuries at a Las Vegas hospital, where he told patrol officers that the incident occurred about 10 hours earlier, according to a police department statement. “There was a delay in reporting due to the victim receiving treatment,” the statement said. The name of the victim, his hometown and a motive for the alleged attack won’t be made public immediately, Officer Larry Hadfield said. Kamara, one of the top running backs in the NFL, is charged with felony battery resulting in substantial bodily harm. Detectives went to the Cromwell hotel-casino, home to the rooftop …