A 10-year-old girl was killed by a shotgun blast in her home in a prosperous upper Northwest Washington neighborhood yesterday, and the girl's mother, who apparently shot herself in the shoulder, was charged with homicide in the girl's death, D.C. police reported.

Lt. William Ritchie of the D.C. police homicide squad said Erin Knight De Veau, a student at Janney Elementary School, was found dead in an upstairs bedroom of her family's two-story brick house at 5112 45th St. NW.

Ritchie said the girl's mother, Leslie A. De Veau, a former teacher and social worker, was found in another upstairs bedroom of the house near Western Avenue in the Friendship Heights area.

Mrs. De Veau, who was taken to the Washington Hospital Center after the shootings, was formally charged early this morning. Police declined to speculate on a motive in the incident.

The husband and father, Anthony H. De Veau, a senior vice president of a Northern Virginia savings and loan institution, drove up to the house about 10:20 p.m. last night, apparently unaware of the tragedy.

Leaving his car on the normally quiet street, which was ablaze with television lights and filled with the cars of police and reporters, he demanded: "What's going on here?" and ran into the house.

Police said they had been trying to find and notify De Veau, who had been scheduled to participate in a business-related panel discussion in Virginia last night.

Friends of Mrs. De Veau said they had expected to play tennis with her late yesterday afternoon and tried to reach her by telephone but found the line busy. They went to the house about 4 p.m. and knocked on a door but could not summon anyone in the family. Both front and rear doors were locked, the friends said.

The only visible response to the knocking came from the family dog, a blond cocker spaniel named Daisy, which came to a window and scratched against a pane.

The friends left to play tennis without Mrs. De Veau, then returned to her home and again could not find her. As concern mounted, other neighbors, who had a key, were contacted, and about 7 p.m., police were called.

Authorities said the girl, who was shot once in the upper part of her body, may have been killed as early as 11 o'clock yesterday morning. They said she did not attend classes yesterday at Janney, where neighbors said she was in the fourth grade.

Mrs. De Veau, wounded in the left shoulder, was listed in serious condition early today in the Hospital Center's shock-trauma unit.

Police said they found an automatic shotgun in the bedroom with Mrs. De Veau.

Neighbors speculated that the gun may have belonged to Mr. De Veau, who they said was a hunting enthusiast.

Friends and neighbors described the De Veaus as a quiet and private couple who had moved to the blue-shuttered house shortly before the birth of their daughter, whose 10th birthday was celebrated recently with a party in the house.

Mrs. De Veau, according to neighbors, held a master's degree in social work, and formerly had been employed as a social worker and as a teacher at a Northwest Washington preschool.

For several hours last evening, friends and neighbors of the De Veaus stood outside the house, watching as investigators went in and out. One of them pointed to a window of the second-floor bedroom where the child's body was found. As police technicians made flash photographs inside, the window filled with brief bursts of brilliant light.