Police are trying to determine what led three Earlham College students to be struck by a train early Friday morning while walking near a group of nightclubs in Richmond. Senior Therese Heymann of Burlingame, Calif., was killed, and the two others had to be airlifted to a Dayton, Ohio, hospital. Classes at the Quaker-affiliated college of about 1,200 students were suspended Friday. Police said the three were out in the historic Depot District of Richmond for the annual College Night event. They were struck about 1:15 a.m.