A man wearing a hood and carrying a gun tried to rob a woman in Loudoun County on Friday in what authorities said may be the fourth such recent incident involving the same man.

On Friday, the county sheriff’s office said, a woman in the Sterling area was walking to her apartment after dark when a man approached, brandishing a firearm.

During the confrontation in the Stanford Square area of Sterling, he demanded her wallet and ordered her to take off her jacket. She screamed, the sheriff’s office said, and he fled.

A similar incident, in the same neighborhood, occurred five days earlier, the sheriff’s office said. A woman returning to her apartment was approached at her door by a man who showed a gun and demanded her wallet.

Those incidents may be connected to December incidents in the Sterling area, the sheriff’s office said. In the first, a woman was approached about 6:15 a.m. Dec. 29 by an armed man who demanded that she drop several items and remove some clothing.

She ran into her house, leaving items behind. A purse was reported missing, the sheriff’s office said.

Later that day, the sheriff’s office said, a robber approached a woman who was unloading groceries in the 10200 block off Mc­Kean Court. He pointed a gun, and she, too, screamed.

He fled, and nothing was reported taken.

Police said he was described as a light-skinned black man in his mid- to late 20s who is about 5 feet 8 with a medium build. He wore a dark hoodie that concealed part of his face and may have used a small burgundy or red vehicle.