PONTIAC, Mich.—A third party will investigate events at Oxford High School that occurred before a school shooting that left four students dead and six other students and a teacher wounded, the Michigan district’s superintendent said, with the Michigan attorney general responding Sunday that her office could conduct it. Oxford Community Schools Superintendent Tim Throne said in a statement that he called for the outside investigation because parents have asked questions about “the school’s version of events leading up to the shooting.” He also elaborated on interactions with the student leading up to the shooting. “It’s critically important to the victims, our staff and our entire community that a full and transparent accounting be made,” Throne said. His comments came after a news conference Friday by Oakland County Prosecutor Karen McDonald that detailed numerous warning signs from the student charged in the shooting: His search for gun ammunition on a cellphone, …