"Everyday, every 28 hours, a police officer or a security officer murders a black person in this country, either a black man, women, children, the elderly, and I am tired of it, and that's why I am here," explained protester Jova Johnson, who lives in Oakland.
Oakland police told ABC7 News that there were no permits issued for Monday morning's action and that it came as a surprise to city planners and law enforcement.
Officers arrested at least 13 people who had chained themselves to the entrances of the police building at 455 Seventh St. starting around 7:30 a.m.
The glass door to one entrance was broken by police tools while officers cut the protesters free, police spokeswoman Officer Johnna Watson said.
NEW: @oaklandpoliceca "OPD Tactical Team was in communication with identified group leaders and worked towards a peaceful resolution."— Nick Smith (@nicksmithnews) December 15, 2014
Protesters had also blocked Broadway between Sixth and Seventh streets, where a group of activists locked themselves together with PVC pipes. Officers in riot gear marched up Broadway at about 10:45 a.m., clearing the street of protesters and arresting those who refused to leave.
A protester also climbed up the flagpole at police headquarters to put up a flag that said "black lives matter," which also depicted the faces of black men killed by police.
The protester remained perched on the flagpole past noon. Another group of protesters had chained themselves to the base of the flagpole and about a dozen more surrounded them.
All of those protesters would be arrested, Watson said. She said police were working slowly and methodically to remove the chained demonstrators so as not to injure them.
As Oakland enters its fourth week of protests following a grand jury's decision not to indict Ferguson, Missouri, police Officer Darren Wilson for shooting and killing black 18-year-old Michael Brown, organizer Cat Brooks said demonstrators had finally reached Oakland police headquarters.
"There's a war on black people and the police are the army in that war," Brooks said. "We are on the precipice ... of a new civil rights movement."
The protesters said every 28 hours in the U.S., a black man is killed by police, private security or a vigilante.
Monday's action was organized by black leadership, including the groups BlackOut Collective, Onyx, Black Lives Matter and Black Brunch, which had previously organized actions that shut down the West Oakland BART station and marches through Oakland's Rockridge neighborhood.
White and Asian protesters locked themselves to the doors in solidarity with the black leadership, according to organizers.
Lucia Lin, 27, stood alongside a group that had chained themselves to the main entrance of the building on Broadway. She said she was part of a group of Asian activists "putting our bodies on the line to shut down institutions committing a war on black people in this country."
"As Asian community members we know historically we've been used to prop up ideologies that have allowed violence against black people to occur," Lin said.
Other groups of demonstrators gathered on Broadway, reading the names of black men killed by police, chanting and singing. A cold drizzle didn't prevent their numbers from surging throughout the morning.
As police used bolt cutters to break the chains on one entrance and arrest the demonstrators, a group gathered around them singing, "I can hear my brothers crying 'I can't breathe'; Now I'm in this struggle saying 'I can't leave'; Calling out the violence of the racist police; We ain't gonna stop 'til our people are free."
The protesters released a list of demands and many held it printed on signs Monday morning.
The demands included the demilitarization of local law enforcement, a comprehensive review by the U.S. Department of Justice of systemic abuse by local police departments, repurposing local law enforcement funds for "community-based alternatives to incarceration," a Congressional hearing to investigate what they said is the criminalization of communities of color and racial profiling, the passage of the End Racial Profiling Act and a national plan of action for racial justice.
Authorities advised motorists to avoid taking Interstate Highway 880 ramps in downtown Oakland, as well as the Posey Tube between Oakland and Alameda, as a result of the protest.
Meanwhile, over the weekend, protesters in San Francisco are advocating that demonstrators "perform their protest," encouraging people to use art and creativity to get their message across, instead of violence and destruction.
In Berkeley, a large group of demonstrators were standing around chanting, when a woman attempted to drive through the crowd.
Protesters hit the car and yelled at her. A few demonstrators opened her car door and argued with her.
A short time later, that woman was able to turn around and drive off.
ABC7 News reporters Laura Anthony and Nick Smith contributed to this story.