LAS VEGAS—After playing in the Pro Bowl on Sunday, Saints running back Alvin Kamara was arrested and accused of beating someone the night before in a Las Vegas nightclub. Police learned Saturday that 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 …