Lt. Cmdr. Norman K. Green, a Navy intelligence officer, returned to his Mount Vernon area home yesterday afternoon and found his 31-year-old wife dead of a gunshot wound and the couple's 2-year-old daughter suffering from gunshot wounds, Fairfax County police said.

Police said their initial investigation indicated that Laurie Jean Green shot her only child, Aimee Frances, two times, then shot herself once with a .38-caliber handgun that she purchased yesterday morning in Woodbridge.

Police said they did not know what Mrs. Green's motivation might have been and that their investigation was continuing.

Aimee Green, who police said was conscious when she was found in a playroom on the lower level of the house, was taken by police helicopter to Fairfax Hospital, where she was reported in critical condition last night after surgery.

Police said Green, 33, called home several times in midafternoon, and when no one answered he grew worried and returned home. After finding his wife and child, he called police.

About 45 minutes after his discovery, a grim-faced Green, still dressed in his starched white uniform, walked from the house at 9008 Greylock St., climbed into an unmarked county police car and was driven to the hospital where his daughter had been taken.

News of the shootings shocked residents of the quiet neighborhood half a block from the George Washington Memorial Parkway and a mile from the Mount Vernon estate.

Suzanne Swet, a 14-year-old who said she babysat once a week for the Greens, remarked to a reporter that "Aimee is really sweet, always giving everybody hugs." When told by police that Mrs. Green was dead and that Amy Aimee had been shot, Swet burst into tears.

Neighbors described the family, who had lived in the home since August, as friendly and apparently happy. They said the family was scheduled to return this summer to California, where Green had been reassigned.

Neighbors said Mrs. Green was seen regularly jogging around the neighborhood and that she and her daughter often played in the yard of their home.

On weekends, neighbors said, the couple often went bicycling on the Mount Vernon bike path, with Aimee riding in a seat on her mother's bike.

Dave Sheleg, 20, who lives across the street, said he spoke occasionally to Mrs. Green and saw her frequently outside with Aimee. "In fact, I never saw the mother without the baby, either on the back of her bike or in the little carriage," Sheleg said. "They were always very happy."