Los Angeles police said the attack happened near 9th Street and Grand Avenue on Nov. 6.
Authorities shared surveillance video they believe captured the attacker in a nearby parking garage.
The man was seen wearing a sweatshirt with the word "thrasher" on it and is seen in the company of a woman wearing a black hat.
Detectives are asking anyone who recognizes the man or the woman to please alert police.
A $50,000 reward is being offered in the case.