Jimmy Lee Dykes told neighbors he was building a storm shelter.
He told one neighbor tornadoes had come dangerously close to destroying his homes in the past.
But that bunker 4 feet below the Alabama dirt became a prison for one young boy named Ethan, surely more terrifying than any storm.
He was held there for six days after being stolen from his school bus by Dykes who killed the driver after demanding hostages.
There are many details that FBI and police officials haven't released about what unfolded during those six days. Nor have they given any details about what was inside the bunker. Was there light? A bathroom? A stove?
Two neighbors who saw the shelter when it was being built told CNN what they remember.
A hatch made out of plywood nailed together with hinges covered the bunker and acted as a door, neighbor Jimmy Davis Jr. told CNN's George Howell. Dykes, who had lived near Davis for about a year-and-a-half, had shown him inside the bunker.
Davis last saw it about eight months ago. Since then, he said Dykes turned violent towards him and his family, and he didn't know what was going on beneath the plywood cover he could see from the road.
It was anyone's guess what was happening inside as the days ticked by with no rescue of the 5-year-old child.
Beneath the plywood hatch, Davis remembers cinder blocks stacked to form a staircase and little red bricks lined the wall.
Michael Creel, who also lived nearby for about a year, saw the bunker as well.
"He'd be up from sunup to well after 10, sometimes past midnight out there moving sand," Creel said of the early construction of the bunker.
Inside the bunker Creel said he saw two-by-fours and two-by-six boards bracing the walls and floorboards. Dykes told Creel that the built-in ceiling protected against the possibility of wet ground above, Creel said.
The inside was wrapped with eight inches of insulation and several layers of plastic, he said.
And in between the brick walls, Davis remembers something else: A PVC pipe that ran from the bunker to the front of Dykes' property.
The kidnapper told Davis while he was building the bunker he wanted to hear people or passing cars coming in case he was trapped in the storm.
But as the nearly week-long saga unfolded, that pipe took on a different purpose.
Police used it to communicate with Dykes along with the telephone inside the bunker and the hatch door. After the rescue, authorities found the pipe packed with explosives along with another explosive inside the bunker itself, authorities said.
Police said Dykes was "contentious" the entire time, but he allowed them to deliver comfort items for Ethan including coloring books and toys.
While they were negotiating with him, officials told the media Dykes used an electric heater and blankets to keep the boy warm.
As the outside world waited to learn what was unfolding inside that bunker, rescue teams found a way to see inside.
Somehow, somewhere, they slipped a camera into the hideout, a law enforcement official said.
On Sunday things began to change. Negotiators sensed a change in Dykes' demeanor. But what they saw through the camera was what made them decide to storm the bunker and rescue the boy on Monday: Dykes was holding a weapon.
That's when federal agents, who had been practicing rescue missions, detonated large explosions and two agents dropped into the bunker shooting Dykes and killing him, sources told CNN.
Ethan, who celebrated his birthday shortly after the rescue, was unharmed. It was all over in seconds.
CNN's George Howell and Martin Savidge contributed to this report.