Hundreds of cars began streaming from the giant complex, including children who had been kept in locked-down schools.
The Texas Army base was the scene of a mass shooting in 2009.
U.S. law enforcement officials say four people, including the shooter, were killed when a gunman opened fire Wednesday at Fort Hood.
One of the officials, citing official internal U.S. Justice Department updates, said 14 others were hurt. The officials spoke on condition of anonymity because they were not authorized to release information by name.