The Tustin Police Department reported that officers responded to a call of a robbery at a residential community in Tustin at approximately 9:36 p.m. (0436 GMT) on Saturday. Tustin is in Orange County, about 55 km southeast of Los Angeles, Xinhua news agency reported.

"Upon arrival, officers learned that the victim was a member of the U.S. Secret Service and that his backpack had been stolen at gunpoint. An officer (agent) fired shots during the incident," the press release said. “There has been no trace and it is unknown at this time if the suspects were injured as a result of the incident.”

The police department said the incident is under investigation, adding that officers found some of the victim's belongings in the area.

Officials said a 2004-2006 silver Infiniti FX35 or a similar vehicle was seen leaving the scene and the police department is asking for the public's help in identifying the subject.

Local news outlets reported that the robbery occurred on the same night that Biden was in downtown Los Angeles for a lavish fundraiser that raised approximately US$30 million for his re-election campaign.