BIRMINGHAM, Ala. -- The mother of an Alabama boy who was snatched off a school bus and held hostage in an underground bunker for days said her son witnessed officers fatally shooting his kidnapper.

Jennifer Kirkland's comments about her son, identified by authorities only by his first name Ethan, came in an interview with Dr. Phil McGraw for an episode of the "Dr. Phil Show" that is set to air Wednesday.

In a promotional clip posted online, Kirkland said her 6-year-old son saw officers shoot the gunman identified as Jimmy Lee Dykes, 65.

"He says, 'The Army came in and shot the bad man,"' Kirkland said.

Authorities said Dykes shot and killed Ethan's school bus driver before grabbing the child off the bus and taking him into an underground shelter constructed on his rural property in southeast Alabama.

The FBI said agents wearing combat gear entered Dykes' bunker on the sixth day of the standoff. Dykes was shot multiple times, a coroner said.

Ethan wasn't physically injured, but his mother said he has had a difficult time sleeping, and she is worried about him.

"I'm scared of how he's going to take getting on a bus," she said.

Kirkland said she wanted to swap places with her son during the standoff but wasn't allowed to. It wasn't clear in the promotional excerpt whether she made a formal offer to Dykes.

"I wanted to be there," said Kirkland.

Authorities have said they might never know why Dykes shot driver Charles Albert Poland Jr., 66, and took the boy off the bus on Jan. 29.

Dykes was due in court the day after the standoff began for a hearing on a menacing case filed in December. Neighbors say he fired a gun at them. Neighbors and acquaintances described Dykes as having strong feelings against the government.