The private law office of Vallejo Mayor Osby Davis caught fire overnight and fire investigators quickly declared the fire suspicious.
Video from the scene Saturday morning showed extensive damage in the front lobby section of the office. The back offices also suffered smoke damage, according to firefighters.
Mayor Davis arrived on the scene while the fire was still burning. He told the Vallejo Times that to say he was upset would be an understatement.
"I plan to keep going," Davis told the paper. "This is a bump in the road, a temporary hurdle. And we'll get past it and continue to do what we need to do."
Firefighters said they got the call about the fire at 1:30 a.m. and when they arrived flames and smoke were pouring from the one story structure in downtown Vallejo.
Fire investigators said they are looking into the possibility of arson.
Vallejo police called in the FBI, and said they treating the fire as a possbile case of domestic terrorism.
NBC Bay Area has learned police have surveillance video from a building across the street . That video is being processed to assist in the investigation.
Construction crews were on the scene by 7 a.m. with a plan to board up the building.