The tip came the way the FBI had long expected - from a family member with misgivings.
But the search for the man investigators now believe is the Unabomber still had months to go, first as a deeply torn family struggled with its loyalties and then as an elite team of agents camped for weeks in the Montana snow.
And even now, the case is far from finished, law enforcement officials said Thursday.
With the arrest of Theodore Kaczynski in Montana, hundreds of agents, held back in recent weeks for fear of somehow tipping their hand to a fugitive who had eluded them for 17 years, are fanning out to airports, bus stations, homeless shelters and universities across the nation.
They are trying to fill the many blanks in the mysterious life of Kaczynski, a Harvard-educated recluse.
The tip that led to the arrest arrived in a similarly mysterious fashion, investigators said Thursday. When Kaczynski’s brother, David, of Schenectady, N.Y., first approached the FBI early this year, his initial contact was veiled.
As described by federal officials supervising the investigation, David Kaczynski, who also had attended Harvard and who helped his brother purchase the Montana property in 1971, grew suspicious late last year that his brother might be the author of the Unabomber’s published 35,000-word manifesto.
David Kaczynski combed old family papers, finding what he feared might exist, copies of some letters dating to the 1970s that were written by his brother to newspapers protesting the abuses of technology. The sentiments were disturbingly reminiscent of what he thought he had read in the Unabomber manuscript. But it was not until January that a lawyer for the family telephoned the FBI in Washington.
“The lawyer was nervous,” one official recalled. The lawyer described the situation without revealing either brother’s name or the basis of the suspicions. “The brother was nervous,” the official added, “wanting to protect and not to smear his brother’s name if he wasn’t guilty and not to hurt him if he was.”
What followed was a delicate dance of persuasion. It took several more weeks to set up a meeting at an FBI office with the lawyer and David Kaczynski, and just before they met, additional writings were turned over that seemed to solidify the connection.
Still, the official said, the lawyer balked at identifying the letter writer or giving his whereabouts. But agents, having learned David Kaczynski’s identity and schooling, had already begun checking his background.
“We had kind of figured before he told us who his brother was, and that they both went to Harvard,” the official said.
Finally, not only did the agents discover Theodore Kaczynski’s mountain cabin, but also were able to persuade his mother to authorize a further search of the family’s house in Lombard, Ill., in mid-March as family members prepared to move out.
Quickly then, postal investigators, FBI agents and explosive specialists, disguised as lumberjacks and other outdoorsmen, began slipping into Helena, and the rural hamlet of Lincoln 50 miles northwest.
The agents began striking up conversations with local residents, hoping to learn more about the hermit in the cabin without tipping their hand. At the same time, a pair of snipers from the FBI’s elite Hostage Rescue Team crept close to the cabin and staked it out for weeks, communicating with their commanders by encrypted radios.
They watched as Kaczynski sometimes emerged to tend his garden and retrieve provisions from his root cellar. But he never left his property. On Tuesday, 40 agents ended the surveillance, converging on his mountain home armed with a search warrant.
The officials said that Kaczynski tried to withdraw inside the cabin, but was restrained.
After his capture, Kaczynski gave no further resistance, but instead, one official said, became “quite personable, and well spoken,” but asked for a lawyer. He declined to answer questions but engaged in pleasant small talk with the agents.
The search for the answers he declined to give is proceeding primarily on two separate, intensive tracks by agents from the FBI, the Bureau of Alcohol, Tobacco and Firearms and the Postal Inspection Service.
One will be an excruciatingly detailed examination of physical evidence investigators can uncover from Kaczynski’s wilderness cabin, seeking links to the mountainous pile of bomb fragments, writings and package scraps collected over the 17-year investigation into the bombing campaign.
Agents have carefully preserved and catalogued evidence from each of the bomb crime scenes, as well as the bomber’s written communications to victims and news organizations, carefully analyzing the mailing labels and stamps.
The other path of inquiry will focus on building what agents call an investigative profile that could provide links in time and place between Kaczynski and the bomber known until recently only through postmarks.
Investigators said they were examining whether Kaczynski traveled by bus in the days preceding the dates when package bombs were mailed from cities far from Montana, like Sacramento, Calif. In addition, they are investigating whether he may have stayed at homeless shelters or inexpensive motels along the route.
Other agents are combing through air travel records to determine whether Kaczynski might have flown from Helena, about 50 miles southeast of the site of his cabin, to the cities from which the bombs were mailed.
Investigators are also interviewing associates and classmates at the universities where Kaczynski studied and worked. After graduating from Harvard in 1962, he earned a doctorate in mathematics from the University of Michigan and taught at the University of California at Berkeley.