Federal authorities could be seen storming the cockpit of a Delta Airlines flight in San Francisco before they placed the co-pilot in handcuffs and led him off the flight. The federal agents entered Flight 2809 from Minneapolis shortly after it landed at the San Francisco International Airport at around 9.35pm on Saturday. They were filmed donning plainclothes and wearing law enforcement badges around their necks. Their faces were cropped out in video shared online. But passengers said the group of 10 officers included agents from Homeland Security Investigations and others who identified as federal air marshals, KTLA reports. 'A group of people with badges, guns and different agency vests/markings were pushing their way through the aisle to the cockpit,' a passenger who was sitting in first class told the San Francisco Chronicle. She went on to explain that the officers 'stormed the cockpit, cuffed the pilot, arrested him, walked him down the aisle and ushered him off the plane through the cabin doors located between first and coach.' Soon after, a second team of agents returned to the plane to collect the unidentified co-pilot's personal belongings. Authorities did not immediately reveal why the co-pilot was apprehended. But Fox News national correspondent Bill Melugin cited a senior federal official who claims the co-pilot was taken into custody by Homeland Security Investigations on allegations involving child sexual abuse materials. The arrest seemed to shock even those who worked on the flight. The remaining pilot said he had no idea what was happening, View from the Wing reports, and a passenger on the flight recounted asking a member of the flight crew what was happening. 'I looked at him and said "What's going on?" He said, "I have no idea,"' the passenger told Fox 9. 'And he genuinely looked like this was a surprise, that all of a sudden there was people on the plane, because he had us stand up, we were starting to take our stuff out for arrival and everybody was already in the overhead bin.' The passenger who spoke to the Chronicle ultimately called the experience 'shocking and unnerving,' noting that those on board received no information from the crew about what had occurred. DailyMail.com has reached out to Delta Airlines and Homeland Security for more information.