July 28 (UPI) -- Passengers reported that a co-pilot was arrested at the San Francisco International Airport after the flight landed.

The incident occurred on Saturday after Delta Flight 2809 landed in San Francisco from Minneapolis as a passenger named Sarah, who only identified herself by her first name, said about 10 federal agents boarded the plane.

"They barged through and stormed the cockpit," Sarah told NBC Bay Area. "They removed the co-pilot, cuffed him, presumably arrested him, and brought him back down the aisle to deplane

A Homeland Security investigator spokesperson said, "HSI was assisting the Contra Costa Sheriff's office with an arrest warrant."

"The remaining pilot and the flight crew also appeared stunned and shocked and said they didn't know what was happening," Sarah said.