The boy, identified only as Ethan, was rescued Monday afternoon when FBI agents rushed the bunker where suspect Jimmy Lee Dykes was holding him. Dykes, 65, was killed in the raid.
Law enforcement officers stormed the bunker after negotiations with Dykes deteriorated and he was seen holding a gun. ABC News said an explosive charge was used to blow open the bunker door.
"I've been to the hospital," FBI Special Agent Steve Richardson said Monday evening. "I visited with Ethan. He is doing fine. He's laughing, joking, playing, eating, the things that you would expect a normal 5- to 6-year-old young man to do."
"He's very brave," Richardson said, "he's very lucky and the success story is that he's out safe and doing great."
Ethan was expected to be released from the hospital Tuesday. He will celebrate his sixth birthday Wednesday.
"I would image it's going to be the greatest birthday that family and that little boy has ever experienced and probably will ever experience," local pastor Michael Senn told NBC's "Today."
Law enforcement officials spent days negotiating with Dykes through a ventilation shaft, which was also used to send Ethan comfort items, including a Hot Wheels car, coloring books, cheese crackers, potato chips and medicine.
Officials inserted a high-tech camera into the bunker to monitor Dykes' movements and he was seen holding a gun. They became concerned that Dykes could do something harmful, a law enforcement source with direct knowledge told ABC News Monday.
"Within the past 24 hours, negotiations deteriorated and Mr. Dykes was observed holding a gun," the Richardson said. "At this point, the FBI agents fearing the child was in imminent danger, entered the bunker and rescued the child."
During a Monday news briefing, Dale County Sheriff Wally Olson said Dykes was injured when officers entered the bunker but didn't say how Dykes died. A law enforcement official told NBC News officials were awaiting the medical examiner's report.
The standoff began Jan. 29 after Dykes got on a school bus in Midland City and demanded driver Charles Poland Jr. hand over two children. When Poland protected the children by blocking Dykes' access to the school bus aisle, the gunman fatally shot the driver four times and grabbed the boy, police said.
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