Federal prosecutors said one of Ronald Andrulonis' colleagues at Amtrak identified him from a selfie and other footage taken inside the Capitol.
The 37-year-old was captured on camera multiple times, including once in a senator's office according to federal officials.
An Amtrak timesheet later revealed that he did not report to work as scheduled that day.
Andrulonis is now facing federal charges for the incident, including disorderly conduct.