Demonstrators marched onto Interstate 880, shutting down all lanes of the highway as they staged a sit-in. At one point, protesters started lighting off fireworks, set a Caltrans sign on fire and even climbed onto a big-rig.
All lanes of I-880 have since reopened.
VIDEO: Protesters set off fireworks on I-880 in Oakland
The CHP issued a Sig-alert for both directions of Highway 880 around 9:10 p.m., asking drivers to use alternate routes. Big-rigs were given permission to use Interstate Highway 580 on a temporary basis.
The large protest gathered at Frank Ogawa Plaza around 7 p.m. in response to the fatal police shootings of Alton Sterling in Louisiana and Philando Castile in Minnesota.
The group quickly grew to about 2,000 people. As the demonstrators made their way toward 6th Street, a group of approximately 1,000 went onto the freeway and blocked traffic in both directions, police said.
PHOTOS: Thousands march in Oakland to protest fatal police killings
Demonstrator Rachele Simmons is from St. Paul and she said she was outraged over what happened. "He was a member of our community up there. He was born and raised, had a great family. And I'm just very upset and I'm embarrassed. I'm embarrassed that something like this happened in my city," Simmons said.
Police have reported vandalism to the Police Administration Building, including paint on the doors, scratches on glass and broken glass.
There have been other incidents of vandalism reported including broken windows and graffiti at nearby businesses, police said. There have been arrests made, but police have not said how many people were arrested during the protest.
On Tuesday, Sterling was shot to death by police in Baton Rouge Louisiana.
Sterling was selling CDs outside a convenience store when police responded to reports of a man with a gun.
Philando Castile died Wednesday after being shot near Saint Paul, Minn. by an officer who pulled him over for a broken taillight.
His girlfriend streamed the encounter on Facebook live.
The graphic video shows Castile bloody and unresponsive in the seat beside her. His girlfriend's four-year-old daughter was in the backseat the whole time.
Bay City News contributed to this report.
Click here for full coverage on recent police shootings.
Broadway & 7th in Oakland shut down, protesters blocking intersection @ OPD. Officers surrounding HQ. pic.twitter.com/3VV4duVc8D— Cbarnard (@CornellBarnard) July 8, 2016