Powell was a member of the Philadelphia PD's bomb squad, and like the "firemen" in Ray Bradbury's dystopian novelette, he was performing a function assumed to be the opposite of his expected role: Rather than disposing of a military-grade bomb, he was using it as a weapon of mass destruction.

The building targeted by Powell was occupied by members of a militant group called The MOVE.  Aerial photographs taken shortly before the May 13, 1985 assault displayed a weapons bunker and large containers of oil on the roof of the row house. So it wasn't at all surprising that a few seconds after Powell heaved his bomb from the open door of a State Police helicopter, a huge orange fireball erupted from the top of the building. The uncontained fire consumed that house and sixty others, leaving the entire neighborhood a smoldering ruin. 

Philadelphia was the only U.S. city to be bombed from the air during the Cold War, and the perpetrator of that attack was not the Soviet Union, the Weather Underground, or some other offshoot of the Soviet-inspired "Tricontinental Movement." The perpetrators of this act of mass terrorism was the Philadelphia PD – with the indispensable help of the FBI and the US military.