More than 80 people were arrested when a downtown rally organized by Occupy Oakland demonstrators got out of control.
Occupy Oakland distanced itself from the overnight violence, saying it was a splinter group of protesters causing the trouble.
Once that group began vandalizing walls with graffiti, lighting firebombs and breaking into a vacant building, police in riot gear moved in.
Phil Tagami stood with a shotgun in the lobby of his office building that had just been renovated by $50 million renovated.
"We were armed and that was a deterrent for keeping them from coming into the building. We basically just had a stand-off, you could say, until the police came to move the rioters, the provocateurs, the anarchists," said Tagami.
Like other downtown Oakland business-owners, Tagami spent the day directing repair crews to fix the damage, replacing panels of windows at $5,000 to $8,000 each, and cleaning off graffiti.
"Mia," who didn't want to give her last name, was volunteering her lunch break to help out.
"I can only do this for a half-hour because it's my lunch break right now," said Mia. "I have to go back to work, but I wish I could be doing it all day."
The trouble followed a relatively peaceful day-long general strike in which Occupy Oakland encouraged people to skip school and work to protest the economic inequality.
It culminated with an impressive march that shut down the Port of Oakland.
But some decided that wasn't enough and got out of control, which upset residents and workers.
"This is really a betrayal of the spirit of social change and revolution in the United States," said Michael Fried, an Oakland music director.
"We are about peace. We are about resolving issues. We are not about terrorism," said Oakland resident Angel Levy.
Derek Winslow was one of more than 80 arrested.
"It was an expression of the frustration people have felt towards the banking system, towards the police," said Derek Winslow, a protester who was arrested.
Asked why the particular building was vandalized when it had nothing to do with the banking system, Winslow replied: "I'm really frustrated that people broke these windows for City Dental right here. Because that's not the type of place people should be targeting."
Instead of issuing a formal apology, Occupy Oakland is telling businesses they regret what happened, and is offering to help.