A 12-year old Prince William County boy, described by a prosecutor as being troubled that he was not being treated fairly by his family, was ordered held without bond yesterday pending a hearing on charges that he shot four members of his family.

"The evidence shows that he had certainly contemplated doing this for some time," Commonwealth's Attorney Paul Ebert said yesterday. Ebert said the youth had previously threatened members of his family.

The youth, the fourth of six children of James and Frances Mandley of Nokesville, a rural community 35 miles south of Washington, was sent to a juvenile detention center in Fredericksburg to await arraignment Aug. 14 on four counts of felonious asssault. He appeared calm during yesterday's brief hearing, police said.

The boy's mother, Frances Mandley, 42, two of his sisters, Joan Swain, 25, and Bonnie Hemingway, 23, and Hemingway's 14-month-old daughter Kelly were found shot with a .22 caliber rifle Thursday in the master bedroom of the family home at 12705 Hazelwood Dr. Mandley and Swain are listed in serious condition at Washington Hospital Center. Hemingway and her daughter are listed in critical condition at Prince William Hospital in Manassas.

Ebert said the youth apparently did not intend to shoot his infant niece, who underwent five hours of surgery for a chest wound. "She was the only one he didn't have any ill feelings for," said Ebert. Ebert said the boy's mother was apparently holding the infant as a shield when they were shot.

Police said they were called to the home by one of the injured and found the youth, unarmed, sitting in front of the house. The youth's father, a meatcutter, and two brothers were not home at the time of the shootings, police said.

Relatives, interviewed yesterday, said the weapon used in the shootings was one of about 40 guns owned by the family, some of which were stored in the youth's bedroom.

"We're sportsmen," said the youth's brother-in-law, Roy Hemingway, 26, whose wife and daughter were wounded. "Like [him], I was brought up as a red-blooded American boy to hunt and fish."

Hemingway and other relatives and neighbors expressed shock at the shootings.

"I still can't believe it," said another brother-in-law, James W. Swain, whose wife Joan was shot. "He got along good with everybody. He was just a normal, average boy."

Authorities said yesterday that the youth will be tried as a juvenile. If convicted, he could be sentenced to confinement in a juvenile institution until his 21st birthday.