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The process, authorities say, is so time consuming that the bomber must be a loner. He may also be, warns San Francisco FBI special agent Jim Freeman, who is heading up the Unabom task force, "a quiet person, a typical 'nice-guy' neighbor."
Quiet, perhaps, but increasingly dangerous. According to former FBI agent Fox, the bomber has refined his technique over the years; the later bombs are more sophisticated, activating only when the package is opened. "He's evolved," says Fox. "This guy's done a wonderful job in self-education."
According to Mark Logan, the assistant special agent in charge of the San Francisco division of the ATF bureau, the bomber may work in a "somewhat eccentric" way at his job, though authorities can't say what that job is. Many suspect he may have some connection to a university. The package that killed Mosser had a fictitious return address typed on it -- "H.C. Wickel, Department of Economics, San Francisco State University" -- that has so far yielded nothing.
While investigators last week continued to dole out information on their progress and to urge the public to call a toll-free hotline with tips (1-800-701-BOMB), the seeming randomness of Mosser's murder left some people wondering if they might be next. Many advertising agencies beefed up their security procedures, and sales of such devices as X-ray metal detectors skyrocketed. Some computer users on the Internet discussed the case in private E-mail messages but avoided the public bulletin boards, loath to call attention to themselves. But John T. Horn, head of corporate security at Kroll Associates, a New York-based security company, is careful to keep the matter in perspective. "It's highly unlikely that you'll get one in the mail," says Horn, who himself fielded dozens of anxious calls last week. "One event doesn't make it an epidemic." Some of those with the most to fear agree. "Sure, it bothers the hell out of me -- like any terrorist act would," says one prominent computer scientist. "But it's not going to change the way I do things." Says FBI investigator Lou Bertram, who worked on the case until he retired in 1988, "the longer he's out there, the better the odds that he's going to be caught. He has to make a mistake."