As the standoff dragged on, an FBI hostage rescue team practiced on a nearby mockup of the bunker until kidnapper Dykes' declining mental state forced them to move in Monday afternoon, law enforcement sources said Tuesday.
The resulting assault -- from the top of the bunker, according to another law enforcement source -- ended with Dykes dead and Ethan free.
The other law enforcement official wouldn't say what exactly was done to get into bunker, but the FBI team didn't go in through the hatch.
Authorities took Ethan to the hospital for evaluation.
"He was running around the hospital room, putting sticky notes on everyone who was in there, eating a turkey sandwich and watching 'Spongebob,' " Dale County Schools Superintendent Ronny Bynum said.
Authorities said Dykes abducted the young boy from a school bus January 29.
Dykes approached the bus and demanded that the driver hand over two children. Dykes killed driver Charles Poland as he blocked the aisle -- allowing children to escape from the back of the bus -- but Dykes seized Ethan and fled to the bunker, according to authorities.
During the ensuing standoff, authorities were extraordinarily tight-lipped about what was happening, but said they were in contact with Dykes and said they believed he had not harmed the boy. He also allowed authorities to deliver food, medicine and at least one toy for the boy to play with, according to authorities.
The details about the law enforcement response to his abduction are the first provided by authorities about how they knew what was going on inside the bunker and why they decided to move when they did.
But many questions remain, including whether the Defense Department provided sensing equipment to aid in monitoring what was happening inside the bunker and why Dykes acted as he did.
'A big boom'
At one point Monday, Dale County Sheriff Wally Olson told reporters that Dykes had "a story that's important to him, although it's very complex."
But according to a law enforcement source, Dykes' mental state deteriorated in the 24 hours before the Monday afternoon rescue.
Experts from FBI units, including a crisis negotiation team, tactical intelligence officers and a behavioral sciences unit, had determined Dykes was in a downward psychological spiral, the source said.
At 3:12 p.m. (4:12 ET) on Monday, the FBI team went in.
While the law enforcement source said FBI agents went in through the top of the bunker, the source declined to say specifically how they breached the roof, how many agents were involved or whether Dykes shot himself or was killed by FBI gunfire.
A Dale County official told CNN that Dykes had been shot multiple times. The body remains "in the area" and will be examined by the county coroner before it is taken to Montgomery, Alabama, for autopsy by the Alabama Department of Forensic Sciences, the official said.
Tom Fuentes, a former FBI assistant director, said the rescue likely was complicated by the layout and materials used to build the underground bunker.
Rescuers would have had to come down stairs, exposing their legs and meaning Dykes would see them first, he said. And if there were brick walls, the FBI agents would have to shoot carefully to guard against ricochets -- all that after probably tossing in a flash grenade to stun the kidnapper.