The bank robber in a ski mask pressed a shotgun to Myrna Opsahl's side and killed her with a single blast, the result of a holdup by a 1970s group known for its revolutionary rhetoric.

According to a later account, the alleged killer claimed the shooting was an accident but that it didn't matter because the victim "was a bourgeois pig anyway."

This week, police and prosecutors moved on homes of quiet middle-aged residents allegedly linked to the 1975 robbery, triggering a court fight sure to revive memories of the revolutionary passions and rhetoric from a different era.

The Symbionese Liberation Army emerged from the ashes of the 1960s anti-war movement and was blamed for several violent acts in the 1970s.

Merging black ex-convicts and middle-class college graduates, the group achieved notoriety for kidnapping newspaper heiress Patricia Hearst and forcing her wealthy parents to donate millions of dollars of food to the needy. The SLA's actions were fed by the rhetoric of militant revolutionaries, together with a passion for minorities and the poor.

Opsahl's routine, dropping off a church collection at the bank, had collided head-on with the radical SLA. Four armed robbers burst into the bank in Carmichael, Calif., shot Opsahl and escaped with $15,000, dropping as much cash as they kept.

Opsahl's son, physician Jon Opsahl, has dedicated much of his adult life to bringing his mother's killers to justice.

"This is very therapeutic, that it did matter," he said after the charges were filed against the former SLA members. "That it matters to a lot of people."

Police in Los Angeles, Oakland and Portland, Ore., arrested former SLA members Emily Harris, William Harris and Michael Bortin on Wednesday morning. Sara Jane Olson, already facing sentencing Friday for a failed 1975 plot to bomb a Los Angeles police car, surrendered to police after she was charged in the robbery. Also charged was former SLA member James Kilgore, a fugitive since the 1970s who remains at large.

One of Olson's lawyers, Shawn Snider Chapman, said prosecutors have built a weak case. "All these people have been snatched from their homes for nothing," he said this week.

Olson went by her given name, Kathleen Soliah, in the 1970s before disappearing and resurfacing in Minnesota. She faces 20 years to life in prison for the bombing attempt, which she said was to avenge the death of six colleagues in a 1974 shootout with police in Los Angeles.

Her brother, Steven Soliah, was acquitted in a 1976 federal trial for the Carmichael robbery.

Hearst, at the center of a kidnapping drama that consumed the world's attention, is expected to be the prosecution's leading witness in the robbery case.

In a 1982 book called Every Secret Thing, Hearst said Emily Harris shot Opsahl. She also named the robbers and lookouts and detailed her own role as a getaway driver.

Hearst wrote that Harris answered a colleague's question about Opsahl's condition by saying, "Oh, she's dead. But it really doesn't matter. She was a bourgeois pig anyway. Her husband is a doctor. He was at the hospital where they brought her."

She explained in the book, "Emily told us the shotgun had gone off by accident. She had told the woman to get down on the floor, but the woman had not moved fast enough to suit Emily. So Emily thrust the shotgun forward to threaten her, and the gun had gone off."

Hearst, Steven Soliah and Wendy Yoshimura were granted immunity for their involvement in the robbery in exchange for their testimony before a 1991 grand jury, Sacramento County District Attorney Jan Scully said.

The long-dormant case has gathered legal momentum since Olson was arrested in 1999 after two decades on the run.

Scully said there was new information in the case, "which we believe establishes additional corroborating evidence linking those named by Patty Hearst to the Crocker Bank robbery and murder."

Affidavits filed in Sacramento Superior Court for Wednesday's arrests said bullets, drawings of banks, robbery instructions and a Sacramento street map had been found at the SLA's San Francisco safe house. The FBI also linked shotgun pellets found in Myrna Opsahl to ammunition from the SLA house.

The files also say Olson's palm print matches prints on the door of a Sacramento garage where the group stored a getaway car.