Barbara Williams, a short, plump black woman with an Afro, sat on the floor in the living room of the Southeast Washington apartment, running her fingers through a stack of records. She was fidgety, and it was evident that the shock of the last 24 hours had not worn off.

"I couldn't sleep last night for thinking about it. I was scared. It's really frightening to think I killed someone," she said, placing a record on the turntable.

Williams, a 23-year-old guidance aide at Hart Junior High School in Southeast Washington, stabbed to death a man who attacked her on a Metrobus Tuesday morning Williams was arrested but the charges were dismissed later in the day because of an insufficient basis for criminal charges.

"I just freaked out when they told me he was dead," she said. "I couldn't believe it. I didn't mean to kill him. I just wanted to get him off of me." b

"My sister isn't a violent person," interrupted Williams' sister. Mary, who had been sitting quietly in a chair watching television and listening to the conversation. "I remember one time some guys were mouthing at us in a carryout and she told me to ignore them."

"People like that you just ignore," Barbara Williams said. "They're sick."

Ignore is exactly what Williams tried to do when the unidentified man started talking to her.

For Williams, it all began shortly before 8 a.m. She left her basement apartment in the 4000 block of Ninth Street SE and started to walk toward the bus stop at the corner of Ninth and Bellevue streets.

She was humming and singing when she saw two teen-age girls running away. She heard screams coming from a parking lot adjoining her apartment building.

As she got closer, she saw a man kicking and beating another man who appeared to be in his 20s or 30s."He kept kicking him, and telling him to call him general," Williams said.

She said the man on the ground who was being kicked had been at the bus stop on other days. But she didn't recognize the assailant.

Williams said she continued on to the bus stop, just around the corner of the building. While she was waiting for the bus, it started to drizzle, so she put up her umbrella. As she did so, she looked up, and there was the man who had been attacking the other man.

"I just hate people who put up their umbrella when it's not raining." she said the man said to her.

The man called her names and cursed at her. He also threatened to beat her. Frightened, she reached in her pocketbook' for a pocketknife that a friend had given her a few years ago for protection.

"I didn't know what he might do," said Williams, who said she placed the knife in a side compartment of the purse where it would be handy.

She said she thought about returning to her apartment, but she was afraid the man would follow her there.

After about seven minutes, the A-2 bus arrived. All -- three Williams, the man who had been kicked, and the man who was harassing her -- boarded the bus.

Williams walked to a seat near the back and sat in the aisle seat. She took out a novel to read. No one was seated next to her.

Two people were seated in front of Williams and other passengers were standing or sitting around. But when the man continued to harass her some of the people seated nearby moved to the front of the bus.

Williams said she continued to try to read her book, "The Stand," by Stephen King, ignored the man, who "was cursing and saying all sorts of embarrassing things. He was talking crazy."

Suddenly, the man spat on her face and hit her just above her lip.

She grabbed the pocketknife from her purse and swung it at him.It struck him in the chest.

Williams said she turned her back on the man in an attempt to get away from him, and as she did so he reached for the pocketknife in her hand.

She heard a male voice yell, "Break it up," and a female voice scream, "Fight sister," but no one tried to help her.

Finally the man sat down and rested his head against the window. The bus driver, a woman, stopped the bus at 200 Atlantic St. SE, and everyone hastily got off while looking back at Williams and the man.

As she got off the bus, Williams said, the man watched her, but didn't say anything.

Still frightened, she said, she "paced back and forth" on Atlantic Street waiting for the police to arrive. The man got off the bus as Williams watched warily, but he made no move toward her. He collapsed beside the front door and died shortly afterward. He was unidentified as of yesterday evening.

"I didn't mean to kill him," Williams said over and over again yesterday.

Williams said she had planned to go to work yesterday, but a supervisor called to tell her she had been placed on administrative leave with pay.

A D.C. school spokesman said the action was taken to give Williams an opportunity to recover from the incident.

A grand jury is investigating the incident, according to the U.S. attorney's office.

Williams, a D.C. native who attended D.C. public schools said she had been working at the school less than a year.

"I don't know when I'll go back [to work]," she said."I hope it's soon. I can't stay around here all day. I have to stay busy . . . That way I don't think about it."