At least a dozen people watched as Karen Beth Green was forced, struggling and screaming, into a car and driven slowly away on a dusty semi-rural road. Two days later, her body was found in a garbage dump on an Indian reservation.

Now the witnesses to her abduction wring their hands in frustration. Several phoned the police, they say, but had they known she was going to be murdered they would have tried to do more.

Green, a resident of Apache Junction, 30 miles east of Phoenix, and the mother of a 5-year-old boy, was filling in for the regular letter carrier when she was kidnaped shortly after 1 o'clock last Saturday afternoon near the Salt River Indian Reservation, which borders suburban Scottsdale and Mesa.

Her burned-out 1963 Plymouth Valiant was found on the reservation Sunday about a mile from the abduction scene. Her body was discovered Monday evening, in a dump three miles from the car.

An autopsy determined that she died of a stab wound to the chest, that her throat had been cut, that attempts had been made to smother her and that she had been beaten on the face and head.

The tale of Green's abduction recalled for many the 1963 murder of Kitty Genovese, a Queens, N.Y., barmaid whose cries for help were heard by dozens, not one of whom went to her aid. Genovese was the victim, it was said, of urban indifference.

But the spot where Green parked her car near a mailbox, on the fringe of the sprawling Phoenix metropolitan area, is hardly a big-city jungle. The roads are dusty, homes are on one-acre-plus lots. There is little traffic, but witnesses say at least six cars passed by as Green vainly fought her assailants.

Horrified witnesses described the abductors as two Indian women and three Indian men. Two Indian children were with them when the kidnaping--and perhaps the killing-- took place.

Residents of the area, fearful that their own lives may be in danger, asked for anonymity as they told of seeing Green's abductors force their way into her car, hearing her scream in terror, and watching as the kidnapers drove away slowly.

"I heard her screaming," one man said. "We had already called the police two times. So I ran out in front of my house, and I shouted at those Indians that we had called the police.

"I wanted that woman to have peace of mind. I wanted her to know that help was on the way. So I stood there screaming my head off."

There was a loaded shotgun leaning against the kitchen wall, and a .38-caliber pistol in a holster next to it.

"You never know what's really happening," the man said. "If I had figured they were going to murder her, I could have jumped in my pickup truck. I always have two loaded guns in it. I could have been over there by the mailbox in a minute."

Authorities were told that five Indians were standing under a big tree near the mailbox, drinking beer and wine.

Another witness told what happened after Green parked a few feet from the mailbox.

"One of the big women reached into the car through the window and grabbed her in a choke hold," the witness said. "The other woman grabbed her, too. All I could see was the mail lady's blonde hair flying everywhere. She just kept screaming and screaming. Then the two women got in the front seat, and the men pulled the mail lady in the back seat with them."

With five adult Indians and two children crowding into the two-door car, Green was forced onto the floor, witnesses said.

The entire incident lasted about 15 minutes.

One witness said "it seemed to take forever" for the abductors to leave with Green.

Mesa Police Sgt. Mike Hayes said six officers were sent to the scene within three minutes of the first call. By the time they arrived, Green's car was gone.

About 400 pieces of mail believed to have been taken from Green were found early Monday morning by a derelict in a dumpster in Phoenix's skid row, a downtown area known as the Duce, about 20 miles from the kidnaping scene.

The FBI arraigned Janet Antone, 31, on murder charges today, and continued the search for four other possible suspects. Postal authorities have put up a $10,000 reward for the arrest and conviction of Green's killers.

U.S. Attorney A. Melvin McDonald said warrants had been issued for four other persons. He identified three of them as Brenda Gail Antone, 30; Clayborn Dale Osife, 41, and Sanford Darrell Chiago, 29. The fourth person was not identified, but McDonald said all five live on the Salt River Indian Reservation.

McDonald declined to elaborate on the investigation, refusing to answer questions about the children who reportedly were at the scene. He also refused to speculate on a motive, but robbery was considered a possibility.

Herschel Andrews, president of the Salt River Indian community, pledged the full cooperation of his law enforcement unit with federal and local investigators. He called the killing "a deplorable tragedy" and expressed the tribe's sorrow and sympathy for Green's family.

Frank Mertely, a spokesman for the Indian community, said officials there are concerned that reports of the crime "make it sound like everybody here is a baddie."

It was substitute carrier Green's first day on that particular rural delivery route. She had worked off and on for the Postal Service since August, 1980, and held two janitorial jobs as well. Her husband, Roger, is a construction worker.