A bystander who rushed to help when an officer was attacked in San Francisco said the suspect "had a death grip on her."
The officer responded Friday evening to a report of a person making threats, and after making contact with the suspect, the suspect assaulted her, the San Francisco Police Department said.
Michael Waldorf said he saw the Asian female officer pull up to the scene, walk over to the suspect and tell him to turn around.
"He turned around put his hands behind his head," Waldorf said, but then, "I saw him grab her, pull her to the ground."
"He had a death grip on her," Waldorf told ABC News. "He was holding on very tightly to her, squeezing her, squeezing her head and pulling her hair."
Several bystanders rushed to the officer's side, including Waldorf.
"I saw that it was an emergency and she was in trouble," he said. "I ran over and immediately tried to free her from his grip -- hitting him in the head."
Waldorf said other officers quickly responded and he stepped aside.
The suspect was arrested, and the officer was taken to the hospital with non-life-threatening injuries, police said.
Waldorf said he wasn't hurt.
Waldorf, who lives in Oregon, said he's well-equipped to respond to the incident -- that he's done crisis intervention volunteer work for 20 years.
"The first responder in me was probably reacting," he said. "I think it's appalling that an officer would be attacked by someone who's reasonably ordering them to do something."
Police said Monday that they're "looking at all aspects of this assault on the officer which includes a possible hate crime."
Police added that they're "greatly appreciative" of the bystanders who came to the officer's aid.
Anyone with information is asked to call the San Francisco police at 415-575-4444.