Until this week, the Shin family seemed like an American success story: Sun Shin ran a thriving aluminum-siding business out of his neatly trimmed split-level home in West Springfield. Daughters Aera, 13, and Jeira, 9, were model students at Fairfax County schools. Sun and his wife Chun Shin celebrated their wedding anniversary last week.

Then last weekend something changed. Neighbors said they noticed the curtains remained drawn, the Shins' pet cocker spaniel was running loose in the neighborhood, and the usual weekend bustle around the Shin family yard was missing.

On Tuesday evening, a family friend discovered the bodies of Chun Shin, 36, and her two daughters hanging from bedsheets in the upstairs hallway of their home at 7928 Jansen Dr.

Yesterday family members, coworkers and classmates were struggling to understand why the three Korean family members apparently hanged themselves, leaving three handwritten notes behind.

"It appears that there was some difficulty with the marriage," said Fairfax Commonwealth's Attorney Robert F. Horan Jr.

"I think the mother spelled that out. There's certainly the element of loss of dignity. It appears to be a very big part of the whole thing."

Fairfax County police said they notified Sun Shin of the deaths of his wife and children late Tuesday at a Prince George's County motel.

"Whatever happened, happened over the weekend," said Robert Ball, Sun Shin's brother-in-law, who emerged from the house filled with relatives yesterday afternoon to talk to reporters. "Everybody's shocked right now."

Ball, who refused to disclose the whereabouts of Sun Shin, 35, said Shin apparently left the house on Saturday and returned Tuesday, perhaps to talk to his wife.

Horan said the note apparently left by Chun Shin was written in Korean and the notes believed to be left by the daughters were written in English. Law enforcement officials declined to provide details of the contents of the notes, which were found near the bodies.

Fairfax County Police Department spokesman Warren Carmichael said investigators believe the deaths occurred almost simultaneously because of asphyxiation due to hanging.

He said the exact cause of death will not be determined until the autopsies have been completed in a few days.

"As far as we're concerned, this [case] is closed," Carmichael said.

"This is not a cultural thing," said Laura Falkenstrom, a Korean employe of the Fairfax County school system who once taught English to one of the Shin children. "Suicide is very, very rare in Korea. In Korea we believe that the family is most important. The individual is not so important. To do away with yourself and your family at the same time -- that is unheard of."

Family acquaintances said the Shin family, like many of the approximately 730,000 Korean Americans in the United States, placed a high premium on material and academic success.

When the family moved to the United States about six years ago, they settled in lower-income housing in Fairfax County's Mount Vernon section, and Sun Shin began to build his aluminum-siding business, according to Falkenstrom. Shin's business prospered, and two years ago the family bought a home in an affluent West Springfield neighborhood.

"They really worked hard," said Ted Culley, a next-door neighbor. "Always cutting the grass. Always washing the car . . . . I really can't believe it."

Chun Shin, who took English lessons twice a week, had worked as a full-time barber at Jerry's Barber Shop in Springfield Plaza for the past year, according to her co-workers.

She "gave no indication that there was anything wrong," said Jim Bailey, 53, a barber at the shop. "It seemed like a well-adjusted family . . . . There was nothing that I could detect that would show anything like this.

"We all joked around a lot with her," Bailey said. "Oh, we'd joke about everything. About going to K mart. About shopping all the time. She'd take her break and go over to K mart. She was just fitting in real good."

Shin talked frequently about her daughters, colleagues said, recalling conversations about how difficult it was to make her daughters do their homework on sunny days and about how her older daughter Aera was growing up quickly.

Aera was a seventh-grade student at Washington Irving Intermediate School, where school officials said she received mostly A grades, was an accomplished artist and cross-country runner, and had several close friends. Principal Raymond Watson said counselors were helping some of those friends yesterday.

"We're trying to ease the pain for the kids as much as we can," said Watson. "There is a lot of frustration that they could not talk with her one more time. Kids seem very eager to talk about it."

Jeira Shin, a fourth grader at West Springfield Elementary School, was a hard-working student, a member of the school safety patrol and an outstanding artist, according to Principal Jane Y. Crim. Jeira Shin designed the covers for a class poetry book and a travel brochure for Hilton hotels, Crim said.

Many of Jeira's classmates learned of her death during the school's early morning TV news show in which students discuss current events on camera while other students watch on television sets in their classrooms, according to Crim, who delivered the news in an on-camera interview.