The powerful blasts at the Boston Marathon finish line Monday underscore why the Federal Bureau of Investigation has spent years refining its “tripwire” system for catching would-be bomb makers before they can build a deadly device.
For years, federal agents have asked businesses that sell materials useful in making bombs to alert authorities to any suspicious orders. The types of tripwires in place have shifted over the years. In the 1990s, law enforcement worried mostly about fertilizer-based bombs after such devices were used in the Oklahoma City attacks of April 1995. In the past decade, chemical-based bombs have come into focus as authorities adapt to the changing threat.
“The tripwires have certainly been successful in the past,” said Don Borelli, a former counterterrorism official at the FBI who now works for Soufan Group.