As it turned out, authorities' decision to rely on every tool at their disposal was a wise one: 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, and also placed another explosive device inside the bunker, the FBI said in a statement late Tuesday.

WSJ: Military tactics, arms, helped rescue Ala. hostage

Murphy says the original design plans were recently discovered, showing how the property was rigged with 200-kilowatt generators, massive air-intake tunnels and a custom ventilation system to be used in the face of disaster.

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