Jack S. Cornejo's best buddy describes him as a social butterfly with "millions of friends" in Falls Church, where he graduated from George Mason High School and still lived with relatives.

Cornejo, who went by "Steve," argued with his pals occasionally, but he never started a fight, family and friends said.

That is why they say they are baffled that Cornejo, 23, got into a violent brawl early Saturday that ended in his death -- and angry that no charges have been filed against the man who killed him with a gunshot to the back.

"He was in the wrong place," said Corina Menjivar, 50, Cornejo's aunt. "What I see is that Steve was like the better guy in the movie. This is not right."

Fairfax County police said they are investigating the shooting, which occurred after Cornejo and another man fought in a Fair Oaks apartment complex courtyard. The shooter, whom detectives have questioned but not publicly identified, still could be charged, law enforcement officials said.

After interviewing witnesses, Fairfax police believe Cornejo and a woman attended a party at the complex. The two emerged from the party about 4:30 a.m. and began fighting, loudly enough to attract the attention of neighbors who were not at the party, sources close to the investigation said. Menjivar said police told her that the woman was "beaten very bad" by Cornejo.

Cornejo and the woman moved to the courtyard of the complex, and one of the neighbors apparently followed them. The neighbor said that he merely wanted to ensure the woman's safety but that Cornejo repeatedly challenged him and then attacked him, police sources said.

The neighbor was carrying a concealed handgun; Cornejo was unarmed. The neighbor told police that as he and Cornejo engaged in a fistfight, he feared for his safety and grabbed his gun. At some point during the struggle, the gun went off, police sources said.

Commonwealth's Attorney Robert F. Horan Jr. has said he is considering whether charges are appropriate or whether, for example, the shooter acted in self-defense.

Family and friends said the story police told relatives does not square with what they knew about Cornejo, an affectionate young man who worked at an Annandale cell phone store and attended church regularly.

"I've grown up with Steve," said Alan Barrionuevo, 22, Cornejo's best friend. "Never in his life has he ever put one finger on a girl."

Menjivar said one witness told her that Cornejo argued with the woman and was "shaking her and telling her to stop screaming" but did not beat her. Menjivar said that when she asked detectives whether the woman was bruised or cut or sought medical help, they said no.

She also said detectives told her the shooter went inside for a gun in the midst of the altercation with Cornejo.

Family members and friends said they cannot understand why the shooter remains free after Cornejo died from a bullet wound in the back -- a sign, they believe, that he was shot when he was vulnerable.

At a Tuesday night vigil, those who knew Cornejo packed into his grandmother's Falls Church house to share prayers and memories, said Kat Arias, 20, a friend of Cornejo. Friends are setting up a Web site and making T-shirts in his honor.

Cornejo was an only child who grew up surrounded by relatives, many of whom emigrated from El Salvador. He was an avid soccer player who stayed away from drugs and gangs, Barrionuevo said.

"He was an example to so many kids who live in the outskirts of our little town," Barrionuevo said. "I really don't want people to see him as just another young Latino male being shot."

Staff writer Tom Jackman contributed to this report.