Law enforcement and others seeking clues into the mind of what now appears to be a serial bomber say the latest explosive incident on Sunday night, the city’s fourth over 17 days, provided more trail crumbs than definitive signposts pointing toward a potential suspect.
Austin interim Police Chief Brian Manley has said preliminary indications are that the newest bomb is similar enough in construction to be connected to the previous three. That doesn’t necessarily mean all were manufactured and planted by the same person.
But if that does turn out to be the case, experts said, the latest attack would slightly alter their profile of the serial bomber’s methods and motive.
Police on Monday said it appears as though a trip wire was used to trigger the latest blast in Southwest Austin, revealing two new important pieces of information about the bomber.
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 who gets hurt is of no consequence to him.”
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.
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.
As a result, Fitzgerald said it’s possible that any of the victims of the first bombs — 17-year-old Draylen Mason and Anthony Stephan House, 39, who both died; and 75-year-old Esperanza Herrera, who was seriously injured — might still be the target of the bomber, with the latest explosion intended only to throw police off the scent.
“It makes it almost seem like the bombings are meaningless, but I still think it means something very specific to him,” Fitzgerald said.
Similarly, experts said, the fact that the newest attack occurred in a neighborhood geographically and demographically different from the other explosions could be part of a deliberate distraction ruse. Yet it could also represent a widening of the bomber’s campaign, signaling that he is bold enough to scout out and work in multiple locations.
Finally, the latest attack suggests that whoever is bombing Austin probably isn’t done.
“A bomb is a statement, but there’s also an element of compulsion to it,” said Brian Jenkins, a Rand Corp. analyst who has studied terrorism and bombings. “Bombers don’t retire.”
Still, experts said the additional attack will yield a new batch of clues that can be mined by the army of local and federal investigators, explosives experts, bomb technicians, evidence teams, chemists, engineers and dogs that has descended on Austin in recent days. Testing has become sophisticated enough that technicians can often trace a small piece of PVC or galvanized steel from a burst pipe bomb back to its manufacturer, said Tina Sherrow, a recently retired senior special agent in the Bureau of Alcohol, Tobacco, Firearms and Explosives’ Chicago office.