SACRAMENTO, Calif. — Sacramento police have arrested a second suspect related to Sunday’s mass shooting downtown, announcing early Tuesday that the brother of the man arrested Monday is now in custody for possession of a firearm by a prohibited person and possession of a firearm. Smiley Martin, 27, is the brother of Dandrae Martin, who was booked into the Sacramento County Main Jail Monday on charges of assault with a deadly weapon and possession of a firearm by a prohibited person, police said. The mass shooting killed six and wounded 12, and police said Smiley Martin was one of the wounded w…