The man charged with setting a fire outside the Vermont office of U.S. Sen. Bernie Sanders had been staying at an area hotel for nearly two months and was spotted outside Sanders’ office the day before and the day of the fire, according to court paperwork filed by a federal agent.

Shant Michael Soghomonian, 35, who was previously from Northridge, California, entered the building on Friday and went to Sanders’ third-floor office where security video showed him dumping a liquid on the bottom of the door and setting it afire with a lighter, according to the special agent with the Bureau of Alcohol, Tobacco, Firearms and Explosives.

The building’s interior suffered some damage from the fire and sprinklers that doused the area with water, but no one was hurt. Sanders, an independent, was not in the office at the time. Seven employees working in the office at the time were unharmed and able to evacuate.

The agent who investigated spotted what appeared to be the remains of a canister of lighter fluid and a red cap on the floor near the office door.

Soghomonian was arrested Sunday on a charge of using fire to damage a building used in interstate commerce, according to the U.S. attorney for Vermont. He had been staying at the Inn at Burlington in South Burlington for several weeks, an employee told authorities, according to the affidavit.

READ MORE Man arrested for setting fire at Sen. Bernie Sanders’ office Sen. Bernie Sanders’s office in Vermont caught fire. Arson is suspected, but the motive is unclear Biden and Sen. Bernie Sanders join forces to promote lower health care costs, including for inhalers

When police knocked on the hotel room door, they heard a male saying he was getting dressed, according to an application to search the hotel room and a vehicle with New York plates. Officers then heard what sounded like the man dragging heavy items near the door. Officers got a key and attempted to open the door but it was blocked, according to the court document. They forced the door open and arrested Soghomonian without incident, they said.

Sanders said in a statement that he is “deeply grateful to the swift, professional, coordinated efforts of local, state, and federal law enforcement in response to the fire” and thankful that none of the people in the office were hurt.

The motive remained unclear. It was not immediately known if Soghomonian had a lawyer, and an initial court appearance had not been set, officials said. A phone message left with the Chittenden County public defenders’ office was not immediately returned. Soghomonian was being held at the Northwest State Correctional Facility in St. Albans.

The crime carries a maximum penalty of 20 years imprisonment and a fine of up to $250,000.

The case was investigated by police departments in Burlington, Shelburne and Williston; Vermont State Police; the Bureau of Alcohol, Tobacco, Firearms and Explosives; and U.S. Capitol Police, officials said.