An off-duty officer was attacked and choked unconscious by several teenagers after he tried to help a woman the group was assaulting, authorities said.

The incident happened Friday outside the Bay Street Mall in Emeryville, about 4 miles northwest of Oakland.

An off-duty California Highway Patrol officer was attacked and rendered unconscious last week by a group of teens after he came to the aid of a woman whose cellphone had been stolen, according to the Emeryville Police Department. Emeryville Police Department

Emeryville police said a woman returned to the mall and confronted a group of teenagers she believed knew the person who had allegedly stolen her cellphone earlier in the day.

The woman asked the teens to give back her phone and the group "became aggressive with the victim and began to assault her," police said in a news release.

In a surveillance video of the incident, the woman approaches the group of at least five teens and grabs one wearing a white hoodie by the arm. He shoves the woman as several other teens gather around her. The teen in the white hoodie shoves the woman again before someone runs over to intervene.

Some of the teens leave as the individual in the hoodie appears to get angry and starts fighting the man who came over to help. The man runs from the group of teens as mall security officers try to break up the melee. The man is later seen lying on the ground but eventually gets up.

Police said the man who intervened was an off-duty California Highway Patrol officer. After he tried to help, the "group of juveniles became aggressive" and "began to violently assault him," Emeryville police said in the release.

"The juveniles struck the Off-Duty CHP Officer multiple times and choked him unconscious," police said.

The officer regained consciousness and pepper-sprayed a teen who was still assaulting him.

Police detained several of the teenagers and arrested two, 14 and 16, for assault.