The area around 14th and Broadway in Downtown Oakland was a busy spot all day. At one point during the afternoon, a large contingent of police officers cordoned off the intersection, accompanied by a huge armored vehicle from the Alameda County Sheriff's Department.
At its largest, the group of protesters numbered in the thousands. Shortly before 9 p.m., police ordered the crowds to disperse. While most heeded the order, some demonstrators who did not were quickly arrested. Others moved through the streets surrounding Frank Ogawa Plaza, breaking windows, setting a few small fires and damaging at least two police cars. Two officers were also splattered with yellow paint.
There were 25 people arrested Tuesday night for things like failing to disperse. That number also included one felony arrest for an assault on an officer and two felony arson arrests -- one of those being for the person who burned a police vehicle.
Earlier in the day, a large group of about 200-300 demonstrators converged on 14th and Broadway and surrounded a small group of officers who had gone in to make an arrest. To control the crowd, police confirmed they set off at least one flash grenade and used tear gas.
ABC7 crews witnessed a man get wrestled to the ground and then Tased by officers trying to arrest him. Earlier, a female protestor on a bike was tackled to the ground by a group of officers and she was handcuffed and taken away.
Police say they are using new crowd control techniques to identify and get troublemakers out of the larger group.
Demonstrators say the police are the ones provoking the violence.
"They plan to turn this into violence like they always have; we're going to defend ourselves, we're not a violent group, but they are a very, very violent group," one protester said.
"We have some flash bangs; they make a lot of noise and that's to deter, to gain the attention of the crowd, so they would stop surrounding the officers," Oakland police spokesperson Johnna Watson said. "That was very effective. We have had some arrests and we've also had some reports of some vandalism."
The vandalism seen by ABC7 crews has been relatively minor -- some bank windows have been sprayed with graffiti and windows on a police vehicle and a news van windshield smashed.
Oakland police say every available officer is on duty and many of them are wearing cameras to document their side of things. Police say there is also mutual aid from other agencies from as far away as Pleasanton.
The tactics Oakland police are using reflect the changes made and lessons learned from previous Occupy demonstrations. The goal is to identify and remove demonstrators police identify as troublemakers before they incite the larger crowd.
"We wanted to send a message that we're not going to tolerate acts of vandalism, violence or any kind of disruption to businesses," Oakland Police Chief Howard Jordan said.
Jordan did say that they will allow people to express their first amendment rights, but they will maintain crowd control.
Other groups that marched in Oakland Tuesday remained peaceful as they chanted in support of workers' rights.
Due to the protests, AC Transit is detouring bus services throughout the city. Click here for a list of route changes.
Laura Anthony, Jonathan Bloom, Lisa Amin Gulezian, Nick Smith and Alan Wang contributed to this report.