A 22-year-old resident of the Potomac Job Corps training center was arrested and charged yesterday in connection with the fatal beating of a classmate in the bathroom of their Southwest Washington dormitory earlier in the day. Officials at the center said the two were friendly and called the incident a "tragic accident."

Samuel Vernard Nanton, of the U.S. Virgin Islands, was charged with aggravated assault. He was arraigned yesterday in D.C. Superior Court.

The incident started with a midnight challenge to a fistfight between Nanton and Thomas Threadgill, 19, of Philadelphia, police said. Soon after, an ambulance crew answering a 911 call found Threadgill unconscious on the bathroom floor. Threadgill was pronounced dead at 12:59 a.m. at D.C. General Hospital, said Sgt. Joe Gentile, a police spokesman.

According to a court affidavit, Threadgill started the fight. Police said they were investigating the cause of the fight.

The center is part of a national program that provides classes to prepare needy, largely undereducated young people for employment.

Many students at the Potomac Job Corps Center, at 1 D.C. Village Lane SW, were in shock yesterday. They told staff members that the fight was not meant to be to the death. Earlier in the day, the pair had challenged each other's strength in the weight room.

"I don't think they went in to do any bodily damage or kill anybody," said Lonnie Hall, director of the center. "This is something no one expected."

Hall provided the following account of the incident after talking to witnesses:

About midnight, the two men entered the bathroom, intending to "prove who was the strongest." They started swinging at each other.

A student entered the bathroom and saw Nanton striking Threadgill several times. Threadgill then hit the wall and toppled forward, and the left side of his face hit a sink. Threadgill tried to rise but fell back to the floor. He then started to shake and have a seizure.

The student who had witnessed the fight started tossing water on Threadgill's face and yelled out for help. Employees called 911.

Both Nanton and Threadgill were well liked and hadn't been in serious trouble before, Hall said.

Nanton had attended the training center for more than three months and was studying business and clerical skills. Threadgill, in the program for about nine months, was studying to become a home health care aide, Hall said.

The program is considered a second chance for many young people who have either dropped out of school or have had trouble learning in mainstream programs. The center in Washington has about 400 students, Hall said.

Students may live on campus or commute. Although there are arguments and fights between students, this is the first time since the center opened 20 years ago that anyone has been killed, Hall said.

The center set up counseling centers around the building yesterday, Hall said. Members of Threadgill's family in Philadelphia also were meeting with grief counselors, Hall said.

The Job Corps began in 1964 as one of President Lyndon Johnson's Great Society programs. Today, there are 119 centers across the country. The program, with 45,000 to 60,000 students, is overseen by the U.S. Department of Labor. Eligibility is limited to applicants 16 to 24 years of age who are living at the poverty level.

The Job Corps has a "zero tolerance" policy on violence and drugs, Labor Department officials said yesterday. Any student who gets into a fight is expelled, they said.

"Both students were aspiring to change their lives," Hall said. "They wanted to become productive members of society."