Police are looking for answers about why a senior at Purdue University shot and killed a teaching assistant in a classroom. The shooting left the college campus about 60 miles northwest of Indianapolis in mourning. Purdue senior Andrew Boldt of West Bend, Wis., died Tuesday. Police arrested fellow senior Cody Cousins on a preliminary charge of murder. Purdue Police Chief John Cox says investigators believe Cousins targeted Boldt. No one else was injured, and Boldt surrendered shortly after the shooting. Cox says there is no immediate indication that Cousins and Boldt had past troubles. Both were students in the engineering school. The shooting prompted Purdue President Mitch Daniels to cut short a weeklong university trip to Colombia and order classes canceled through Wednesday.