Keith Caldwell was the smarter of the two, friends said, a more avid athlete, dependable, more sensitive. His 20-year-old fraternal twin, Kevin, was troubled and couldn't hold down a good job, according to a neighbor.

The brothers were constantly arguing in the hallways of 1430 L St. SE, where they lived and grew up, and the arguments inevitably would lead to a fight, residents of the apartment building said.

"Neighbors would try to break it up, yell at them that it's not right for brothers to fight," said a resident who did not want to be named. The pleas rarely had any effect, she said.

About 9:30 p.m. Tuesday, an argument rang through the stairwells of the four-story apartment building, neighbors said. When fire department paramedics arrived, according to D.C. police, they found Keith stabbed in the left side and took him to D.C. General Hospital, where he died about an hour later.

Kevin Caldwell was arrested a short time later by Prince George's County police on a warrant charging him as a fugitive from the District, D.C. police said. He waived extradition hearings, they said, and yesterday was charged by D.C. police with second-degree murder in connection with his brother's slaying.

A change came over the Caldwell twins about two years ago, neighbors said, when their mother, Hilda Caldwell, died in an apartment fire in the same building.

"Keith was trying to pull his life together, to get off the street. He was under a lot of pressure," said a 19-year-old neighbor who attended Hines Junior High School and Eastern Senior High School with the brothers. She said that after his mother's death, Keith joined the Army Reserves and the Job Corps.

According to Marnette Dean, who lives in an apartment on the fourth floor of the building, "Keith was always pulling his brother along, taking him out and buying him clothes, giving him money."

But Kevin, she said, never got over his mother's death, and seemed to be haunted by memories of the fire in which she perished.

That night, Dean said, Kevin was in the apartment when the blaze was discovered and tried to rescue his mother. But he was trapped on the balcony of their third floor apartment, she said.

"She was hollering in the window, but Kevin couldn't get to her," Dean said. "You could see her fingerprints, her hand prints, where she was scratching at the glass, trying to get the window open." Kevin finally had no choice but to jump from the balcony, she said.

"Kevin had problems after that. You just couldn't talk to him in a normal conversation. He had a negative attitude all the time."

Though the twins had a stormy relationship, Dean said, "there was a special bond, thanks to Keith. Anything his brother wanted, Keith got for him. He kept their bond tight. He said to me, 'No one is going to look out for my brother but me.'