Brave bystanders rescued a San Francisco cop who was pummeled to the ground by a deranged homeless man — who one witness said had her in his “deathtrap.”

The Asian officer had been responding to a call on Friday evening in Chinatown about the man, who was later identified as Geraldo Contreras, making racially motivated threats, news station KGO-TV reported.

Surveillance video showed she ordered him to face away from her and put his hands on his head, which he ignored.

The pair tussled before the man pushed her to the ground and climbed on top of her, prompting a bystander to run over shouting, “Get off of her! Get off of her!”

Others quickly joined to help.

“He’s a big guy, he was not letting go. He had a deathtrap on her. And he was not letting go,” Michael Waldorf, who had just finished eating dinner nearby at the R&G Lounge, told the news station.

“I saw it as an emergency. She needed our help and she needed it right away,” he continued.

The officer, whose identity has not been released, suffered a bloody nose and minor injuries, KGO-TV reported.

Police have not said whether the attack is being investigated as a hate crime.

Contreras allegedly had made threats the day before, saying he “specializes in killing Asian people,” KGO-TV reported.

The San Francisco Police Officers Association thanked the bystanders who intervened.

“We’ve seen a rise in violent attacks by homeless individuals, including attacks on police officers,” the union said in a tweet.

“We are deeply grateful to these citizens who rushed to our officer’s aide. Our staffing shortage left this officer working alone instead of with a partner.”