Washington, Feb 5 (IANS/EFE): The kidnapping of a five-year-old boy in a bunker in Alabama ended Monday with FBI agents shooting and killing the abductor and rescuing the child unharmed, authorities said.

Steve Richardson, the FBI special agent in charge in Mobile, said that agents decided to act when they determined that negotiations with kidnapper Jimmy Lee Dykes had come to an impasse.

"Mr. Dykes was observed holding a gun. At this point the FBI agents, fearing the child was in imminent danger, entered the bunker and rescued the child," Richardson said.

Dykes had built the underground bunker in which he holed up with the boy for seven days.

The child was uninjured, although he was taken to a nearby hospital for a complete medical exam, Alabama state Rep. Steve Clouse said.

Last Tuesday, Dykes attacked a school bus near Midland City and shot the driver to death before abducting five-year-old Ethan, who suffers from Asperger syndrome, a mild form of autism.

Dykes' motives are unknown.

His bunker had been stocked with food, had electricity and a television, along with blankets and electric heaters, and so authorities feared that the standoff could go on for quite some time.

Witnesses told CNN that on Monday afternoon they heard explosions and what could have been rifle shots near Dykes' property shortly before authorities announced that the kidnapper had been killed.