17-Year Search, an Emotional Discovery and Terror Ends

Patrick J. Webb cautiously entered Theodore J. Kaczynski's Montana shack, leading a team of bomb experts. In the gloom, he examined shelves crammed with baby-food jars and baking soda cans that were carefully marked with the chemical names of explosives. Then, in a Quaker Oats box, agents found what they had hoped for: 23 bomb igniters, each made from a piece of appliance cord pulled through a wooden plug. They were unique to the Unabomber.

For Mr. Webb, who saw his first Unabom crime scene in 1982, fresh out of bomb school, and his last in 1995, when he examined the shredded body of Gilbert B. Murray in a Sacramento office, it was the instant of realization that, after 17 years, the F.B.I.'s quest for the serial terrorist had ended. An exultant whoop echoed down the snowy slopes.

Mr. Webb radioed the Federal Bureau of Investigation's forward command post at a nearby sawmill. Jim R. Freeman, the top agent at the bureau's San Francisco office, and Terry D. Turchie, the agent in charge of the more than 100 agents on the Unabom case, rushed to the cabin. Mr. Webb held pieces of wire and other evidence in his hands. Tears streamed down his face. ''This is it,'' he told the two agents. ''It's over. This is the guy.''

Today, in Sacramento, Mr. Kaczynski was sentenced to four life terms and 30 years in prison as the confessed Unabomber.

In a series of interviews over the last week, in Atlanta, San Francisco and Sacramento, agents, prosecutors and retired F.B.I. employees talked for the first time, recalling the details of their work on the 17-year series of bombings that killed 3 people and injured 22.

By the time of Mr. Kaczynski's arrest, the bombings had helped change the way Americans travel and how they use the mail. But the epic investigation had also changed the F.B.I., bringing to law enforcement powerful new tools.

Reconstructing the bomber's movements over two decades, agents compiled a data base that eventually included nearly a million names. Supercomputers searching for patterns spit out thousands of names to examine for leads.

Old Persistence And Computer Searches

But the investigation's missteps and dead-ends also provided powerful reminders of the importance of old-fashioned persistence. For years, agents dreaded the endless assignment. Computer searches turned up little because agents focused on men 10 years younger than Mr. Kaczynski.

But supercomputers, borrowed at first from the military, created vast banks of possible suspects. In an effort to track the Unabomber as he moved west, from northern Illinois to Utah to California, the computers produced thousands of names of people who had lived in all three areas. Each was studied and eliminated.

Mr. Kaczynski's name was in the data base, but the investigators operated on a false assumption: they were correct in looking for a white man but not in thinking that he must have been in his late teens or 20's when the bombings began.

''We felt strongly that his origins were in Chicago and that he gradually moved west,'' Mr. Freeman said. ''How could we know he went to Harvard when he was 16 years old?''

Agents followed leads up hundreds of blind alleys, onto college campuses, into airline offices and public libraries, in a case that became so complex that the job of one squad of investigators was training new agents arriving on the case.

Experts prepared victimology studies for clues to the perpetrator. Behavorial scientists theorized the bomber was a blue-collar loner with a metallurgical background, or a well-educated political militant with a grudge. Agents crawled through junk yards to track down a 20-year-old Fiat Spyder in Utah because one was seen near the scene of a 1987 bombing.

Printing Manuscript Led to a Major Break

In the end, the crucial lead came from Mr. Kaczynski's brother, David, a social worker in upstate New York. David Kaczynski's wife, Linda Patrik, a professor, became suspicious after the F.B.I. began concentrating its investigation on places where Theodore had lived. When David Kaczynski and Linda Patrik read the Unabomber's bitter anti-technology manifesto in late 1995, they decided to alert the authorities.

The role of the Kaczynski family has led to a widespread impression that agents stumbled around in the dark for 16 years until David Kaczynski turned in his brother.

The agents on the case say that impression is wrong. They believe that the Kaczynskis would have never come forward had not The New York Times and The Washington Post decided to comply with Mr. Kaczynski's demand to publish his 35,000-word manifesto. Only The Post printed the document, but its publication was jointly sponsored and financed by The Times. Within the F.B.I., that decision, which the agency had encouraged, was highly controversial, but one that the agents credit with solving the baffling case.

''I believe we took advantage of his mistakes,'' Mr. Turchie said. ''I believe we focused the public. I believe that David responded to that just as we would have hoped, and he called us and he did not say, 'My brother is the Unabomber.' He said, 'I saw this set of information, I have this to offer you. Here it is.' And from that point on we did what we're supposed to do.''

David Kaczynski's lawyer, Anthony P. Bisceglie, said the F.B.I. deserved credit for solving the case, along with David Kaczynski and Ms. Patrik.

Mr. Turchie was an unorthodox choice for the job of running the Unabom investigation. He had started his career as a nonagent support employee but soon became an agent working in places like New York on counterespionage cases. He was known as smart, well organized, persistent and a good team player. ''He was a good thinker,'' Mr. Freeman said. ''I didn't want a traditional door-kicking criminal agent.''

Agents had come to be wary of a Unabom assignment. The investigation had sputtered for more than 15 years without a strong lead. Evidence was spread in offices from Chicago to California in files of the F.B.I., the Bureau of Alcohol, Tobacco and Firearms and the Postal Service. One behavorial scientist argued that one of the early victims was himself the Unabomber. ''Everybody had a theory but nobody had a fact,'' said Donald Noel, the agent who led a squad that investigated and reinvestigated Unabom attacks.

But Mr. Turchie took over as the case was heating up and the F.B.I. was reorganizing the Unabom team. In June 1993, after a six-year hiatus, the Unabomber sent mail bombs to the home of Charles Epstein, a geneticist in California, and David Gelertner, a Yale computer science professor, at his office in New Haven.

With Mr. Turchie's arrival, agents would no longer rotate in and out of the investigation, reporting to an inspector who was responsible to superiors far from the case, in Washington. The team would be permanently based in San Francisco, with agents who would reinvestigate every bombing, reexamine their previous assumptions, looking for fresh information. Mr. Turchie reported to Mr. Freeman, who supervised the case from in San Francisco.

In December 1994, after more than a year without a bombing, the Unabomber struck again, mailing a lethal bomb to Thomas J. Mosser, an executive at a public relations firm in North Caldwell, N.J. It was the first fatality since the owner of a computer rental store in Sacramento was killed in 1985. ''It was sort of a sick feeling in the pit of your stomach,'' Mr. Noel recalled, ''a feeling of impotence.''

New Attacks and Letters, And Finally the Manifesto

The Mosser killing was followed five months later by another deadly attack in Sacramento, in April 1995, that killed Mr. Murray. It came five days after the bombing of the Oklahoma City Federal building.

''Every time you'd think there can't be more pressure, it would go up again,'' said Joel A. Moss, the agent in charge of the team that evaluated suspects.

The renewed attacks coincided with the Unabomber's beginning to send agents written material, sometimes taunting them, as in one letter that called the F.B.I. ''a joke.'' But each letter was a potential lead to the bomber's thinking and whereabouts. In June 1995, the Unabomber sent his manifesto to The Times and other publications.

The manifesto ''sparked a furious debate,'' Mr. Moss said. Efforts to identify libraries that had all of the books cited in the manifesto proved another blind alley. Interpretations and behavorial analyses of the tract had led nowhere. ''Opinions on the manifesto were as broad as the backgrounds of the people who looked at it,'' Mr. Noel said. The agents were left with a choice: find a publisher, as the Unabomber demanded, or withhold the manuscript.

''We were elated to get a demand,'' Mr. Freeman recalled. ''At that point we were thinking, 'We're going to catch this guy because he was acting like an extortionist and we almost always catch extortionists.' ''

But some agents argued that publishing the document would in effect be capitulating to a terrorist. At a long meeting in Mr. Freeman's office, senior agents decided against publication -- but then went to Mr. Turchie's office and, in an informal session, began to rethink their decision. By late afternoon they were back in Mr. Freeman's office, advising him they had changed their minds.

The agents began preparing a lengthy memo for Attorney General Janet Reno. Mr. Turchie and Mr. Freeman went to Washington to meet with senior representatives of the The Times and The Post, which decided to publish the manifesto. ''We always realized that this was never an attempt to get the bombings to stop,'' Mr. Moss said. ''It was that we thought that there was someone out there who knows who the Unabomber is. There had to be.''

The Washington Post printed the manifesto on Sept. 19, 1995. Agents staked out the two San Francisco newsstands that carried the paper. When an unkempt-looking man bought the paper, the agents followed, trailing him to a small apartment in a San Francisco suburb. Their hopes dissolved when they learned he was a writer who had been already investigated and eliminated.

An Angry Essay Points The Way to Montana

The suspicions of the Kaczynski family, first passed to the F.B.I. through an agent in North Carolina named Michael J. Harrison, did not immediately arouse unusual interest among the Unabom team, which in January 1996 was winding up examinations of several promising suspects. As usual, the agents were comparing the suspects' whereabouts with dates when the Unabomber was known to have placed or a mailed a bomb.

''We had a couple of suspects that many people believed were the Unabomber,'' Mr. Noel recalled. Besides, the investigators had received hundreds of similar tips from relatives people claiming the Unabomber was a relative. ''The idea that there was somebody who knew who the Unabomber was, was not unusual,'' Mr. Noel said.

But David Kaczynski had found an angry 23-page essay his brother had written in 1971. Initially, hopes faded when the F.B.I. crime lab determined that the typewriting did not match a machine known to have been used by the Unabomber. But Molly Flynn, an agent in the Washington field office who had read the manifesto, pressed investigators in San Francisco to read the essay.

Mr. Moss remembered Ms. Flynn's apologetic call asking him to examine the essay. ''She just didn't want to let it go,'' he said. ''I said why don't you fax it to me, I'll read it. It sat on my desk until the end of the day. When I finally did read it, a lot of things jumped out. It was the most significant document I had ever seen.''

Within days, Mr. Freeman had dispatched Mr. Noel and four other agents to Montana. They rented used trucks, kept a low profile and for days did not go near Mr. Kaczynski's cabin; aerial photographs had determined he was living at the place his younger brother had described.

The team checked bank records, shopped at local stores for hardware that the Unabomber used, and examined hotel records to match them with dates dovetailing with periods when the Unabomber would have been traveling to cities from which bombs were mailed.

Back in San Francisco, agents filled in the blanks. Kathleen M. Puckett, a psychological expert, compared more of Mr. Kaczynski's writings with those of the Unabomber, ultimately finding more than 150 similarities, and preparing a time line tying Mr. Kaczynski's travels to the Unabomber's. In a rented office in Helena, Mr. Noel taped butcher paper along the walls, filling in the chronology of Mr. Kaczynski's activities. He kept the operation small, and contrary to later accounts, the operation was low tech.

Debate continued about whether Mr. Kaczynski was the right man. Mr. Noel argued with Mr. Freeman. He doubted that anyone living without much money or transportation, in a remote cabin without electricity, could have built the bombs and traveled throughout the West to mail them. But Mr. Freeman was convinced. He telephoned F.B.I. headquarters on April 1. ''I said, this is definitely the guy.''

As Justice Department lawyers argued whether they had enough evidence for a search and arrest, Mr. Freeman ordered the arrest to go ahead. News organizations, including the CBS program ''60 Minutes,'' had learned of their suspect. Mr. Freeman sought approval directly from the F.B.I. Director, Louis J. Freeh. Mr. Freeman said, ''Louie says, ''File that search warrant, you've got ample probable cause.' ''

On April 2, nearly 100 agents flew from San Francisco to Montana to back up an arrest team that was kept small to avoid an armed confrontation. The next morning, a subzero day when the snow crunched noisily with each footstep, a SWAT team took more than an hour to encircle the shack. Shortly after noon, Mr. Noel led the arrest team, accompanied by Thomas McDaniel, the resident F.B.I. agent in Montana, and Jerry Burns, a veteran forest service officer who knew Mr. Kaczynski and was at home in the Montana woods.

As they reached the cabin, Mr. Burns hailed Mr. Kaczynski. When Mr. Kaczynski appeared at the door, he looked disheveled in threadbare trousers with shoes that seemed to be falling apart. Mr. Noel remembered thinking, ''My God, that's what been eluding us all these years.''