A man armed with a 12-gauge shotgun and a 9-mm pistol held a woman and her two children hostage yesterday during a four-hour confrontation with Leesburg police in which shots were fired but no one was injured, authorities said.

William Arvello, 32, whose address was not available, was charged with three counts of abduction, discharging a firearm in an occupied dwelling, and breaking and entering, Lt. M.J. McVeigh said. Arvello is being held at the Loudoun County Adult Detention Center in lieu of $50,000 bond.

About 5 a.m., Leesburg police said, a man shot his way into the Cavalier Arms apartment occupied by Barbara Lavender and her two children, Jonathan, 4, and Nathan, 5. After a standoff with Leesburg police and the Loudoun County Sheriff's Department tactical team, a man, later identified by authorities as Arvello, walked out of the third-floor apartment about 8:45 a.m., hands in the air.

Police said the motive for the incident was unclear. Arvello did know the Lavenders, McVeigh said.

Leesburg police Officer Clagett Moxley arrived at the scene on Washington Street shortly after receiving a call about shots being fired. He found several shotgun shells in the hallway of the building and the door to the apartment extensively damaged, police said. According to police, the assailant shot his way into the apartment after an attempt to force his way in with a crowbar failed.

Police evacuated about 20 people from the apartment building. Seven escaped by using ladders supplied by the local fire and rescue squad. Officers then began telephone negotiations with the suspect, whose mood swayed back and forth from docile to hostile, McVeigh said. At several points, the man allegedly fired shots inside the apartment, but injured no one.

Although hostage situations in Loudoun County are rare, McVeigh said, the incident illustrates that Leesburg is no longer a sleepy town where crime does not occur. "A lot of people move to Leesburg thinking that they can leave their doors unlocked and that they have escaped crime," McVeigh said. "The percentages are lower, but we have every type of crime that that Washington, D.C., has."

Lavender could not be reached for comment.