A Loudoun County man allegedly shot two people, one fatally, late Saturday after they were thrown out of a private high school graduation party for his daughter at a neighborhood swimming pool in Herndon and they returned with guns, a witness and Herndon police said.

A 16-year-old male who was shot in the chest was taken by friends to Columbia Reston Hospital and then by helicopter to Inova Fairfax Hospital, where he was pronounced dead at 7:35 yesterday morning, Herndon police Capt. Darryl C. Smith said. The other, a 21-year-old male shot in the lower abdomen, was taken to Inova Fairfax Hospital by helicopter and underwent surgery. Police said last night that he was listed in critical condition.

Smith said last night that police would not release the name of the man who allegedly did the shooting or those of the two who were shot until today. He said no arrests had been made. The Loudoun man was questioned for several hours by police and then allowed to go home, according to his brother.

A police detective said authorities had not been able to question the 21-year-old because he was still recovering from surgery.

Police released few details about the incident.

The shooting occurred shortly before midnight at the Four Seasons club, a private community club and pool in the 1200 block of Herndon Parkway, where the Loudoun man was hosting a party for his daughter, who had graduated from Park View High School in Loudoun County.

The girl's uncle, who asked not to be identified for fear of retaliation by friends of the shooting victims, said yesterday that family members told several people who showed up uninvited that they had to leave, "but three of them went into the woods and came back with guns." He said one of the intruders held a gun to the head of a nephew.

"I grabbed the guy," the uncle said. "I was sure I was going to be shot."

He said his brother then opened fire in the short stairway leading from the front door of the club to a lounge and deck where the party had been. The uncle said that he escaped injury but that two of the intruders were shot. Police could not confirm that there was a third intruder, and if there was, it was unclear what happened to him.

"It's a bad feeling," said the uncle, still struggling with his emotions yesterday, 12 hours after the shooting. "Why couldn't they just let her have her party?"

The girl's uncle said his brother had a license to carry a concealed weapon, which he said his brother needed as security for his job in auto sales. Virginia is one of 31 states that allow people to carry concealed weapons if they meet minimal standards, such as passing a background check and taking a gun safety course.

The main restrictions under Virginia law are that concealed weapons cannot be carried into schools, churches and courthouses.

Herndon police senior Sgt. John W. Orpin, a detective investigating the shootings, said that for quiet, suburban Herndon, the incident was "very unusual."

Police declined to comment on the account given by the girl's uncle.

The Four Seasons club and adjoining pool are run for the benefit of 683 families who live in the community, a mix of detached single-family homes and town houses. Joyce Burd, secretary of the recreation association's board of directors, said there has never been gunfire at the club in the 18 years she has lived in Four Seasons.

Burd said the club had been rented by a relative of the graduate who is a Four Seasons resident. The relative paid $175 for the use of the club and pool plus a $350 security deposit for the party, which the relative had indicated was to have 50 guests.

Burd said she first was called to the club about 9:30 p.m. Saturday by the two 16-year-old female lifeguards at the pool, who asked her to explain to the family giving the party that they had to leave at midnight. Burd said the family had assumed the club could remain open until 1:30 a.m.

Burd said that she volunteered to remain at the party with the lifeguards but that the lifeguards' parents volunteered to stay. "I was a little uneasy, feeling that I didn't see a lot of adults, but a lot of kids," Burd said.

At 10:30 p.m., a parent of one of the lifeguards called Burd to say that someone had summoned police to the club because of trouble in the parking lot and that the family had decided to send all the guests home.

The girl's uncle said yesterday that when he arrived shortly before 11 p.m., "there were about 18 to 20 girls at the party, and I counted about 100 guys," many of them in the parking lot.

The lifeguards soon went home, leaving the family to clean up.

The uncle said the police officers left soon afterward when they got another call, but before the parking lot had been cleared.

Then more arguments broke out, the uncle said, and the three men with handguns approached the club's front door.

Police said at least five shots were fired. It was unclear whether any were fired by the shooting victims. Yesterday, as community residents were allowed to use the pool, police continued to look for bullets that might be buried in the walls or stairs of the clubhouse.

The uncle said he and his brother talked to police for several hours. He said that his brother was not charged and went home but that the man did not wish to be interviewed. "He is still kind of shook up," the uncle said.