Robbers sometimes try to conceal their appearance, but in two cases in the District last week, victims’ recollections led to arrests, according to police accounts. One arrest was made by a high-ranking police official and another came two months after the robbery occurred.

On Thursday, a man was approached about 11:30 p.m. at a gas station in the 1800 block of West Virginia Avenue NE. When the man, who was trying to pay for gas, refused a request for money, police said a robber snatched cash from his hand and ran.

A description of the robber was broadcast, police said, and Andrew Solberg, the commander of the 5th Police District, spotted a suspect and made an arrest on a charge of robbery by snatching.

In the other case, police said a smartphone was taken by force in a Sept. 10 robbery in the 4100 block of Kansas Avenue NW.

On Sunday afternoon, police said, the robbery victim stopped an officer in the 3500 block of 14th Street NW and reported spotting the alleged robber on Perry Place. Authorities said an arrest was made.