Tennessee ? A fourth person was arrested Friday in connection with the killing of a young man, whose burned corpse was found dumped along railroad tracks, and the death of his date, who was kept alive for days and raped, authorities in Knoxville said.

All four suspects were being held on federal charges, Knoxville police spokesman Darrell DeBusk said. Two were arrested in Knoxville and the other two in Lebanon, Ky.

The victims, Christopher Newsom, 23, and Channon Christian, a 21-year-old University of Tennessee student, were last seen the night of Jan. 6 while on a date.

The two had been at a friend’s apartment and had left to get something to eat, with the plan of then going to another friend’s home to watch movies. They never arrived.

Newsom’s body was found the next day. He had been shot and his body set on fire along a rail line, Chief Deputy U.S. Marshal Rich Knighten said. His girlfriend’s vehicle was found nearby.

The suspects were arrested Thursday and Friday.