An FBI statement late Tuesday said Dykes had planted an explosive device in a ventilation pipe he'd told negotiators to use to communicate with him on his property in the rural Alabama community of Midland City. The suspect also placed another explosive device inside the bunker, the FBI added.
Dykes appears to have "reinforced the bunker against any attempted entry by law enforcement," FBI special agent Jason Pack said in the statement providing significant, new details about how it all ended.
When SWAT agents stormed the bunker to rescue the boy from the man's property in the rural Alabama community of Midland City, Dykes "engaged in a firefight with the SWAT agents," Pack added.
Officers killed Dykes, said an official in Midland City, speaking on condition of anonymity because the official wasn't authorized to discuss a pending law enforcement investigation.
According to the FBI, bomb technicians scouring the Dykes property in southeastern Alabama found the two explosive devices.
The devices were "disrupted," Pack said, though he did not say whether that meant they were detonated or disarmed.
Officers will continue Wednesday to sweep the 100-acre property and, when they finish, investigators can more thoroughly investigate, Pack said.
For days, officers communicated with Dykes through a plastic pipe that rose up from the bunker, which was similar to a tornado shelter and apparently had running water, heat and cable television.
On Monday, authorities said, Dykes had a gun and appeared increasingly agitated, though it's unclear exactly how his behavior changed. Negotiations — the details of which have not been made public — were deteriorating. The Midland City official said law enforcement agents had been observing Dykes with some sort of camera, which is how they saw that he had a gun.
Pack declined to get into specifics, but confirmed that high-tech surveillance equipment was used during the police standoff.
Agents stormed the bunker. Neighbors said they heard what sounded like explosions and gunshots. Agents whisked the boy to safety and left Dykes dead.