What had been a mostly-calm day of protest turned violent overnight, and the protesters themselves expressed concern about what this does to their message. City officials are still tallying damage from Wednesday evening, but they say their strategy of a minimal police presence worked until a small splinter group took matters into their own hands.
The real problem began around midnight when a small group of demonstrators took over a building that was once the office of the Travelers and Society, an agency that helped the homeless. The building now sits empty.
The group apparently set a dumpster on fire in front of the building, painted graffiti on the walls, broke windows and punched a hole in the roof. The group had plans to stay there for the long-term, but they were finally evicted by police.
"When a small group of very violent protesters tried to take over the situation, we were able to arrest them and protect our city," said Oakland Mayor Jean Quan.
Police say they fired tear gas and bean bags into the crowd.
Officials with the Oakland Police Department displayed dozens of items -- including rocks, swords and shields -- that they say a renegade group of protesters used against them.
"We didn't want it to be violent," said demonstrator Derek Winslow. "It wasn't the best reaction, but we are frustrated."
Winslow was one of the demonstrators arrested and said he had no regrets about how things went down.
"I didn't destroy any property yesterday," Winslow said, "but destruction of property is not violent."
In the end, Oakland did have to call for mutual aid and 400 officers from 14 other agencies got involved before things settled down early this morning.
"They were all over the place, sweetie," Quan said when asked where the police were. "It was very hard -- it's a big city. They were in the 100 block."
The trouble came after a mostly-peaceful day of demonstrations in downtown Oakland that ended with a massive march to the port, which was closed for some time. In the afternoon, there were some instances of vandalism, including broken windows at several banks.
The damage done last night has left some small business owners frustrated and angry.
"Outside of the fact that I do support the 99 percent, this is my baby," said Oakland business owner Shari Rivers, who found her coffee shop vandalized Thursday morning.
But Rivers isn't blaming what happened last night on the protesters.
"I totally blame this on the city," Rivers said. "The way things have been handled is totally out of control. This doesn't even look like anything that happens in the United States."
Members of the Occupy Oakland demonstration left signs at businesses apologizing for the vandalism and said they didn't do it. Some members of the Occupy movement tried to clean off the spray paint as commercial steam cleaners sprayed down walls.
City councilman Ignacio De La Fuente believes the destruction could have been avoided.
"I believe it was because of the mayor's and the city administrator's directive for the police to stand down and be invisible and not present," De La Fuente said.
Dom Artozarena, president of the Oakland Police Officer's Association, surveyed the many broken windows at the police substation near Frank Ogawa Plaza.
"I think if we would have (taken care) of this thing early on, possibly. It's hard to say," said Artozarena when asked if police could have prevented the vandalism.
"It was heartbreaking to wake up in the morning to see what happened," said demonstrator Elizabeth Gregg. "The people who did this are not representative of this community."
Campers at Frank Ogawa Plaza share that frustration. They spent today trying to figure out how to kick out unlawful protesters they believe are marring the movement. The problem is, they don't know exactly who all of them are.
"I don't want to label them as a particular group," said Oakland Police Chief Howard Jordan. "We are calling them anarchists...people who want to start trouble regardless of the situation, whether it's peaceful or not."
Peaceful occupiers met on Thursday to discuss how they can kick out the so-called anarchists out of their movement. They said last night's violence was a wake-up call that they need to become more organized.
Quan noted that many of the demonstrators at the camp helped calm things down. Quan said her staff communicated with demonstrators via Twitter.