D.C. police obtained an arrest warrant yesterday for a suspect in the slaying of Sonya Grillo Durham, a teller who was shot in the head during a robbery at a branch of the National Bank of Washington Thursday morning.

The suspect was identified as William O. Hughes Jr., 26, of no fixed address. Hughes was described by police as about 5 foot 7, with a drooping mustache and a scar on his upper left cheek. Police said he should be considered armed and extremely dangerous.

The warrant for his arrest asserts that he is wanted for felony murder committed Thursday during the commission of an armed bank robbery, police said. Sources close to the investigation said that the bank lost about $20,000 in the robbery.

Police conducted an intensive search yesterday for Hughes, concentrating on five addresses where the suspect was known to have lived with family and friends in recent years. Neighborhood traffic was blocked off in at least one area for more than an hour yesterday afternoon while a police special operations team, armed with rifles and dressed in riot gear, fruitlessly searched a town house at 30 Hanover Pl. NW, near North Capitol Street.

Law enforcement officials at area airports, bus terminals and train stations have been alerted to look out for Hughes, homicide officials said.

Police said they obtained a warrant for Hughes' arrest after they received several telephone calls from people who said they recognized the robbery suspect from pictures shown on television and published in newspapers.

Police and witnesses of the Thursday morning robbery at the National Bank of Washington branch at 301 Seventh St. NW said that the shooting was unprovoked. Durham, 36, who bank officials said had been instructed to cooperate in the event of a robbery, handed money over to the robber as he demanded. Moments later, according to the victim's coworkers, Durham was fatally shot for no apparent reason.

Her stepsister, Carmen M. Marrero, 30, wept as she told a reporter yesterday that "she always said that if she ever got held up, she would give the robber all the money he wanted as long as he didn't hurt her."

"She was a fun person to be with," said her cousin, Julio C. DeVillar, 28. " She was very loving . . . got along with everybody."

Durham, who leaves a 14-year-old daughter, was born in the District and graduated from Sacred Heart Academy. She worked at the Industrial Bank of Washington for about seven years as a teller before joining National Bank of Washington. She continued her education while sending her daughter to private school, and was studying computer science at the University of the District of Columbia.