It happened just after 11 a.m. on SW Maynard Road, between Old Apex Road and W. Chatham Street.
Police said witnesses told them 24-year-old Benny "Derrick" Dimery of Old Maxton Road in Laurinburg, N.C. drove around the stop arms on the Maynard Road railroad crossing seconds before the Mitsubishi Galant he was driving was hit.
Dimery was listed in critical condition Thursday afternoon. His girlfriend, 21-year-old Lauren Webb - also of Laurinburg - was killed in the crash.
No one on the Silver Star train #92 was hurt. About 291 people were on board.
A section of SW Maynard Road is closed near Old Apex Road. Traffic is currently being detoured.
Investigators said Dimery could face charges if he drove around the stop arms.