Susan Cummings, the millionaire heiress to an international arms fortune, reached a settlement yesterday morning with the son of the Argentine polo player she shot and killed five years ago.

Lawyers for Cummings and Justin Bonnell, the 10-year-old son of Roberto Villegas, agreed not to disclose the amount of the settlement, which was announced as jury selection was due to begin in the trial of the boy's wrongful-death suit against her.

But Cummings, 40, the usually reserved daughter of late weapons mogul Samuel Cummings, appeared elated, grinning widely as she walked arm in arm out of the U.S. District Courthouse in Alexandria with her mother, Irma.

Cummings's attorney, Blair Howard, would say only, "You know what had been discussed before" -- referring to the $140,000 offer Cummings made to the boy last year.

Justin's mother, Margaret Bonnell, a Colorado roofing contractor and former polo player who dated Villegas for six years in Florida, did not look happy, pursing her lips and saying nothing as she left the courtroom.

Yesterday's settlement in the $15.35 million civil suit halted a highly anticipated sequel to the May 1998 criminal trial in which Cummings was convicted of voluntary manslaughter for shooting Villegas, her employee and lover, in the kitchen at her 300-acre estate in Warrenton.

A Fauquier County jury gave her a 60-day sentence. With time off for good behavior, she served 51 days, with special jail accommodations.

At that trial, Cummmings said she acted in self-defense, alleging that Villegas, a popular figure on Fauquier's polo circuit, attacked her with a knife Sept. 7, 1997. Prosecutors said that Cummings shot him as he was eating breakfast and that the cuts on her arm were self-inflicted.

Justin's mother fought for 2 1/2 years against his father's mother and sister to have the boy named sole beneficiary of the Villegas estate, with the right to file the civil suit claiming emotional damages. Cummings's attorneys said they would have argued in court that his relationship with Villegas, who moved away shortly after Justin's birth, was minimal.

Warrenton Town Attorney James Fisher, who has been following the civil suit, said the defense would have tried to convince a jury that the Bonnells were fortune-seekers.

"I think it would have been very likely of her lawyers to go after the credibility of the plaintiffs as people possibly driven by ulterior designs such as greed," he said.

Bryan Slaughter, one of Justin Bonnell's attorneys, said he and his mother are glad it is over. "It's always bittersweet because you want to go to trial, but you also want to protect your client," he said.

Susan Cummings was convicted in 1998 of voluntary manslaughter for shooting Roberto Villegas, her employee and lover, in the kitchen at her 300-acre estate in Warrenton.