The first is that the new form of detonation indicates the person making the explosive has a higher level of skill or sophistication, said Fred Milanowski, the Bureau of Alcohol, Tobacco, Firearms and Explosives’ special agent in charge of the Houston field division.
The earlier bombs, which were hidden in packages, appear to have been detonated by movement devices, which would complete a circuit when the package was lifted or tilted, experts said. The latest incident means that investigators now must contemplate a bomber capable of using multiple methods to start an explosion, perhaps even by timer or remote control.
A trip wire, which typically works by stringing a taut string across a pathway, detonates a bomb when a person pushes into it. Stringing a wire across or near a route used by multiple people could introduce a new element of randomness to the attacks, said James R. Fitzgerald, a former FBI profiler who worked on the Unabomber case.
Employing a detonating device that doesn’t target any particular person would indicate a dangerous capriciousness and callousness, he said — the bomber “wants to strike out at some perceived wrong, and anyone
By mixing his targets — from specific people who receive a package on their porch to anyone who stumbles by — the bomber could be trying to spread general fear and unease throughout the city, Fitzgerald said.
Or he might be purposefully trying to distract from his real intention.
What You Need to Know: Austin Package Explosions
That was the case when, in December 1989, an Atlanta attorney named Robert Robertson was killed when he opened a brown package he received at home. Investigators at first thought his death was connected to a virtually identical fatal bomb detonated at the house of federal Judge Robert Vance two days earlier. But they later learned Walter Moody had killed Robertson as misdirection.