Police are investigating a sexual attack and robbery late Tuesday night on a woman in Northwest Washington.

The assault took place about 11 p.m. in the 400 block of Q Street NW, police said.

According to authorities, a man put a gun to the victim’s back and forced her into an alley off of Q Street.

The man allegedly sexually assaulted the woman, then stole her backpack, wallet and keys. The attacker ran off after the attack, police said.

It is unknown if this incident is related to other recent attacks in the District, police said. Police described the assailant as a black man in his mid-20s with a medium build, wearing a black leather jacket, a black hat and dark pants.

Investigators ask that anyone with information about this or other sexual attacks in the area call 202-727-9099 or 888-919-2746, or text a tip to 50411.