The FBI hostage rescue team practiced on a nearby mockup of the bunker until Dykes' declining mental state forced it to storm the bunker, law enforcement sources said.
The assault Monday afternoon came from the top of the bunker, a law enforcement source said, and left Dykes with multiple gunshot wounds.
The discovery of the bombs later seemed to further illustrate the danger Ethan faced.
Olson said the bunker will be destroyed once all evidence has been collected.
"This has been a terrible tragedy for this community and I'd hate to see this happen again. No one should see this place," he said.
Ethan was reunited with his mother, who has not been publicly named, at a hospital Tuesday. The grateful mother released a statement describing the reunion.
"I can't describe how incredible it is to hold him again," she said. "Ethan is safe and back in my arms -- and I owe it all to some of the most compassionate people on Earth."
His classmates can't wait to see him, said Parker, the principal.
"We are just looking forward to the time that he can come back in and we can wrap our arms around him and tell him we love him," he said.
Another person grateful was Aaron Poland, whose father was killed trying to protect Ethan and 21 other children on the school bus.
Ethan's made him feel like his dad's final route was finished, Aaron Poland said.
"Ethan was home with his mom. Safe," he said.
"My dad's key job was to make sure that every child was delivered safely to their parents."