Investigators say 45-year-old John Dennis Gillane then barricaded himself inside the Wal-Mart for two hours before he surrendered to police.
Authorities say the man will be charged with three counts of attempted murder.
One of the wounded employees was a manager. The victims are expected to survive.
Investigators have not yet established a firm motive for the shooting, but they suspect it was related to Gillane's pending termination.
