Hayes Singletary Jr. had a passion for boxing that wouldn't wane. Even after having second thoughts about the sport after the death last year of a friend in the ring at the Hillcrest Heights Gym, he came back to his training at the same place.

The 19-year-old, who graduated in 1984 from Potomac High School near Temple Hills, sandwiched workouts at the gym just inside Prince George's County between jobs at the Ramada Inn in Oxon Hill and Hertz Rent A Car in Hillcrest Heights.

Then last Thursday, in what one of Singletary's friends said "must simply have been fate," the Temple Hills resident stepped from the ring after five rounds of sparring, talked with his trainer and collapsed. Singletary never regained consciousness and died Monday at the shock-trauma unit of the Washington Hospital Center.

The cause of death, according to a preliminary report by the D.C. medical examiner's office, was "acute subdural hematoma," or a brain clot. The report said the injury was accidental and occurred during "boxing rounds."

Dr. Frederick Finelli, the surgeon who treated Singletary at the Washington Hospital Center, said yesterday in an interview that the boxer's injury appeared to be caused "by one punch or several punches" that occurred fairly recently.

Singletary had been boxing off and on since high school, his first cousin, Henry Singletary Jr., said, and had hopes of turning professional and emulating his idol, Hector (Macho) Camacho.

"His father said people told him Hayes was a pretty good boxer," Henry Singletary said.

He stopped training for long periods only twice that his cousin remembered. Once was last year, after his friend, John Kevin Gordon, 18, collapsed and died after a light sparring session. The D.C. medical examiner's office listed Gordon's cause of death as an irregular heart beat. The most recent interruption in Singletary's training came several months ago when he broke his wrist.

"He stopped for a little while after his friend died," Henry Singletary Jr. said. "He told us that if anything like that ever happened to him, he didn't want to feel any pain."

Singletary's parents declined to comment about their son's death, but his cousin said the boxer had complained in recent weeks about having headaches. About two weeks ago, Henry Singletary Jr. said, one of Hayes Singletary's employers telephoned his mother because the young man was complaining about headaches and was vomiting on the job. The family was concerned about his boxing because of the headaches.

"That's something we don't understand," he said. "Why would he be in the ring to get hit upside the head if he's complaining about headaches?"

Singletary's trainer, Chris Cline, declined to talk about the incident. Cline earlier had told the Prince George's Journal that Singletary never complained to him about headaches. "If he had told me he had a headache, I wouldn't have let him train," Cline told the Journal. "What happened to him did not happen to him in the gym."

Finelli said he did not know what happened during Singletary's last sparring session and could not say with certainty that the injury happened in the ring. But he said the injury "obviously" was not the result of punches to Singletary's head over a long time.

"If someone comes in with a big cut on his head, and you find out he was just in an auto accident, you have to figure that the cut was obtained in the accident," Finelli said. "You have to take the obvious. We're not talking about something that occurred over a period of time. This is not the case. The injury happened from a blow, and the blow is recent."

Injuries to boxers, especially to the brain, led the American Medical Association to call last December for a ban of boxing, both professional and amateur. The AMA reached the decision, according to a spokesman who asked not to be identified, because "several studies showed clear results of brain damage in a population of boxers. Boxing is unique," the spokesman said, "in that the goal of boxing is to knock out your opponent. That causes brain damage."

Amateur boxers usually wear protective headgear in the ring to absorb some of the impact of blows to the head. Singletary was wearing such gear during his sparring session, his cousin said. But the AMA spokesman said his organization's position is that wearing protective headgear does not address the problem. "You'd have to encase the head in pillows" to cut off damage to the brain, he said.

James D. Merrick, who has operated the privately run Hillcrest Heights Boys Club Inc. since the early 1960s, said that Singletary and Gordon are the only two boxers who have died while training in the gym that is part of the clubhouse. Merrick said the boxers' trainers, who work as volunteers, actually run the gym. Merrick declined to comment about the Singletary case.

Hayes Singletary's close friend, Deana Clemmons, 20, said Singletary wanted to be a professional boxer.

"It was his dream," Clemmons said. "I know he loved his boxing. It must simply have been fate. There's no one to blame."