MENOMONIE, Wis.—Four people found slain in an abandoned SUV in a western Wisconsin cornfield had been shot and were all from Minnesota, authorities said Tuesday of a case they described as a mystery. Preliminary results of autopsies performed Monday by the Ramsey County Medical Examiner’s Office showed the two men and two women all died of gunshot wounds, the Dunn County Sheriff’s Office said. The victims were identified as Matthew Isiah Pettus, 26, Loyace Foremann III, 35, and Jasmine Christine Sturm, 30, all from St. Paul; as well as Nitosha Lee Flug-Presley, 30, of Stillwater. Dunn County Sheriff Kevin Bygd said during a news conference Tuesday that authorities don’t believe the person or people responsible for the killings are local or still in the area. He said investigators do not have a motive. “That one is a mystery,” he said. Authorities believe the four Twin Cities-area residents died less than …