Weather Underground activist Katherine Boudin--a fugitive for 11 years--was captured Tuesday night after a bloody armed robbery in a New York City suburb that left two police officers and one armed guard dead.

Arrested with Boudin was Judith Clark, a Weatherman who served time for her participation in the 1969 "Days of Rage" in Chicago, and two men whose political backgrounds are unknown. Other suspects are still being sought.

Police declined to speculate on the motives for the robbery, except to say they "have not ruled out" political ones. After the identification of Boudin and Clark today, police raided what they said was a New Jersey bomb factory where diagrams of six New York police precincts were found.

The FBI also is taking an active interest in the case because "there have been other bank robberies in upstate New York with a similar MO," FBI spokesman Lane Bonner said.

The four arrested have been charged with three counts of murder after a robbery, and charges related to the police chase and shoot-out in Rockland County, an affluent area 25 miles north of here.

In the $1.6 million robbery, three men armed with shotguns and automatic weapons opened fire on a Brink's truck outside a bank, and later fled, with their accomplices, in a car and a truck.

The truck--in which Boudin was reportedly riding--was stopped at a roadblock by police. Two police officers were killed in the gunfire that followed. Three robbers escaped, stealing cars to do so.

As Boudin ran north on the southbound lane of a freeway, she was captured by off-duty officer Michael Koch. Koch, who frisked and cuffed her, said Boudin was unarmed and seemed concerned for her safety.

"She was yelling, 'Don't shoot me; he shot them. I didn't,' " Koch said. The suspect refused to say anything more, he said.

Koch described the shoot-out scene as "chaos" and said the robbers "shot directly at passengers in cars, they could care less."

He said he was preoccupied with a mortally wounded policeman at his feet.

"An officer died when I was trying to revive him . . . . He lay on the ground with a chest wound . . . with his lungs hanging out . . . . An officer was shot at point-blank range.

"I didn't sleep all night, it bothered me, what can I say . . . . "

Boudin, 38, who gave a pseudonym at the time of her arrest, was later identified by police through a fingerprint check.

She is being held without bail with the other suspects, Clark, 32; James Lester Hackford, 31, and Samuel Brown, 41. Brown, according to a report by United Press International, has a "lengthy criminal record that included a robbery conviction."

The robbery took place Tuesday afternoon and shocked the small community of Nyack, which lost two of its 22-officer police force in the shoot-out at a roadblock about five miles from the site of the holdup, the Nanuet National Bank.

A Brink's truck, with three armed guards, had just made a pick-up there, when, according to witnesses, three men armed with shotguns and automatic weapons opened fire on the guards as they made their way to their truck. One guard was killed, one was wounded in the head, and the third was shot in the shoulder.

The robbers, driving off in a van, took $1.6 million with them, police said.

The robbers, according to police, later split up and drove off in two vehicles, a U-Haul truck and a car. The truck was stopped at a police roadblock on the New York State Thruway.

Witnesses said that when police stopped the vehicle, and pulled two suspects from the front, they were surprised by three others who burst from the rear and opened fire.

The New York Times quoted one bystander who witnessed the shooting of a local officer, 45-year-old Waverly Brown, known as "Chipper."

"The door swung open and one came out shooting and shot Chipper," he said.

Another described the shooting of the second officer, Sgt. Edward O'Grady.

"They shot him in the back--they didn't have to do that."

The suspects then commandeered cars, throwing out passengers, and escaped.

Police, however, recovered the stolen money from other vehicles used in the bank robbery.

There seems to be evidence that the robbery did indeed have political connotations--from both sources inside the police and persons familiar with the radical left. Police and FBI officials said the holdup had led them to a raid on a bomb factory in East Orange, N.J., that uncovered a manual on the construction of bombs as well as diagrams of six area police precincts.

One of the cars used in the robbery attempt, a white Oldsmobile, was reportedly traced to that apartment. Another car used in the robbery, a Honda, was reportedly registered to a woman who had been arrested last month during a clash betwen police and anti-apartheid demonstrators at Kennedy Airport.

And a source familiar with the old radical left and once a part of its workings told The Washington Post that Boudin and Clark were, to the best of his knowledge, part of a splinter group of the Weathermen that had decided to stay below ground, rather than give themselves up.

He also said that while Boudin was the better known of the Weathermen, "Judith Clark is the leader who would have outranked Kathy Boudin." Clark was heavily involved with the Weatherman Central Committee, he said.

The source said that the Weathermen had apparently split two years ago over "inversion--the policy of surfacing and coming up and continuing the struggle"--or remaining underground, and that "the schism was also over the use of violent means, as well as some minor left-wing ideological fights."

He could not elaborate on "violent means" but said that the Weathermen had divided into at least two groups.

The "Prairie Fire" group, which advocated surfacing, had included "many of the names the public associates with the Weathermen," the source said, such as Bernardine Dohrn, Mark Rudd and Bill Ayers.

Both Boudin and Clark are believed to have belonged to the other main group, the "May 19th Movement," which takes its name from the birthdates of Ho Chi Minh and Malcolm X.

Boudin is the daughter of prominent attorney Leonard Boudin, who has represented persons identified with radical causes. Leonard Boudin's New York office this morning told callers he "has no comment" and "he's unavailable."

Katherine Boudin had been sought for 11 years in connection with an explosion that leveled a Greenwich Village townhouse. She had been indicted with Clark in the Chicago "Days of Rage" and, at one time, was on the FBI's most wanted list.

In Washington, FBI spokesman Bonner said a FBI warrant charging her with "unlawful interstate flight to avoid prosecution for mob action" had been dismissed in May, 1979. Cook County, Ill., authorities said today they are still interested in prosecuting Boudin on aggravated battery and conspiracy charges stemming from her 1968 Chicago Democratic National Convention activities.

Whether there are other outstanding charges against Boudin, such as any state charges pending in New York, could not be determined.

Similarly, little is known at this time about Clark, and whether she was forced to go underground, or, like some Weather activists, did so in order not to become involved with grand jury or other police investigations.

Born in New York City, Clark was 21 when she was indicted in 1970 for violation of a federal anti-riot law.

One year later the government admitted it had tapped her phone "during the course of a national security surveillance of a telephone installation to which she initiated calls or from which calls were initiated to her." Clark filed a suit against the government in 1978. At the time of her arrest yesterday, she was reportedly living in Manhattan.