A woman was robbed on the street near Capitol Hill late Saturday night, but passersby took action, chasing down and holding someone until officers could arrive, according to the D.C. police.

As the police described the incident, the woman was walking south on 13th Street NE about 11:10 p.m. when a man approached from the opposite direction.

He grabbed her purse, the police said, and tried to take it. But it was strapped around her, and she tried to break free. Then, police said, she saw that the robber had a knife, and she surrendered the purse.

Meanwhile, police said, passersby saw the struggle. The suspect ran, but they ran after him. In a back alley in the 300 block of 13th Street, they grabbed someone, the police said.

Officers were flagged down by another passerby, police said, and they took charge of the matter.

An arrest was made, police said, and they credited it to “courageous actions” on the part of citizens who stepped in to help.

Police said the robbery victim was uninjured, as were the passersby who went to her aid.

It was not immediately clear whether the purse or the knife were found. The site of the incident is a residential street, about two blocks north of Lincoln Park, on the eastern edge of the Capitol Hill neighborhood.

It could not be learned whether any of those involved knew each other.