After avoiding public attention for the better part of a decade, Katherine Boudin and other members of a "terrorist infrastructure" have blown their cover and handed law enforcement a big break in one spectacular and bloody bungle, an FBI official said today.

As Boudin sat in her jail cell, facing charges that could bring her a possible life sentence and separation from her infant son, thousands of uniformed police officers filled Nyack, a normally quiet Hudson River village. They had come today to pay their last respects to men she and other radicals are accused of killing.

As the investigation stemming from Tuesday's attempted robbery of a Brink's truck, in which two policeman and a Brink's guard died, brought one revelation after another of safe houses, links to other crimes and organizational relationships, Boudin remained an enigmatic figure at the eye of the storm.

Those who had known her during her decade underground continued to express shock that she would be involved in such a violent act. They described her as "intelligent," a tireless, even driven debater of causes, and a woman whose conscience was "fired and kilned" in the civil rights movement.

They painted a picture of an intellectual, an honors graduate of Bryn Mawr, dedicated to helping the downtrodden. And yet, this is the second time in her 38 years that her past has intersected a scene of violent death. She was last the focus of public attention in 1970, as she fled the scene of an explosion at a Weather Underground bomb factory in Greenwich Village. Three of her fellow radicals died in the blast.

Just as that bombing helped send Boudin's Weather Underground into hiding with a steadily shrinking membership, her alleged involvement in the Tuesday robbery now has given lawmen the tools and the opportunity to finally break the remnants of the radicals' operation that has eluded them for so many years, at least in the eyes of some officials.

Kenneth Walton, head of the FBI's New York office, said at a news conference today that the $1.6 million Brink's job, in which the Black Liberation Army also has been implicated, has tipped investigators to a network of crimes, safe houses and domestic groups working in concert that officials believe must have been leading up to some kind of offensive.

He said his office is investigating possible links between the coalition of various domestic left wing groups and the Irish Republican Army, among other groups abroad, although there is no hard evidence of such connections. But in answer to a question, he said, "I don't think there is any doubt" that those involved in the Tuesday Brink's robbery are connected to the Puerto Rican FALN group, among others.

"There has been some question as to whether this is a resurgence of the old left," Walton said of the Brink's job and the escalating manhunt that has flowed from it. "I don't really think it ever went away."

During the day, other fugitives were being hunted in the investigators' expanding dragnet, and two radicals arrested Friday were arraigned. Ten suspected radical safe houses have been raided during the last few days and more raids are expected.

"It's anybody's guess" as to how many other crimes the Weather Underground and associated groups have committed, Walton said. He said the crimes apparently were used to bankroll violent groups such as the Black Panthers.

But thanks to the failed bank robbery near Nyack Tuesday, he said, authorities are close to "breaking the back" of the underground network. "When somebody makes a mistake, we capitalize on it."

Walton said the foul-up has enabled lawmen to make more progress in one week than they had in years.

The underground groups are "bent on destroying American society as we know it," he said, adding he thought that ironic since Boudin was found to have been collecting welfare checks from that society.

The two persons captured late Friday were Jeffrey Carl Jones, 33, a Weather Underground fugitive, and Eleanor Stein Raskin, 35, whose address was found on a piece of paper in a Weather Underground safe house, according to police.

Jones and Raskin, sought in connection with the operation of a bomb factory police raided in Hoboken, N.J., in 1979, reportedly had lived in relative obscurity in New York with their 4-year-old son.

Authorities did not link them to the Brink's heist.

Police also said that Nathaniel Burns, arrested in a shoot-out in Queens Friday, was identified as the man whose alias, Sekou Odinga, was signed on a prison registry on the day Black Liberation Army leader Joanne Chesimard escaped.

Authorities also said they were intensifying their search for Marilyn Buck, who was linked to the Black Panthers. She escaped from a federal prison in West Virginia, where she was serving time for federal firearms violations, in 1977. Officials believe she recently had been at the safe house they raided in East Orange, N.J. following the Brink's robbery.

FBI officials also said they were stepping up their hunt for Chesimard, Silas Bissell, a Weather Underground fugitive, and Katherine Power, another fugitive with links to the Weather Underground.

In Nyack, where the funerals of officers Waverly Brown and Sgt. Edward O'Grady took place at the Pilgrim Baptist Church, flags flew at half-staff, stores were closed and streets blocked off. Tight security was maintained.

Inside the church, relatives sobbed as a choir sung the Battle Hymn of the Republic. Outside, 3,000 officers stood at attention.

The Rev. O.T. Moore Jr., the church's pastor, said in his eulogy: "They lived as brothers ought to live. They worked as a team ought to work. They were slain as heroes together."

In South River, N.J., slain Brink's guard Peter Paige was mourned as a "man who died for no reason at all."