Jeff Chiu, Associated Press
A group of people raise their arms while chanting "Hands Up, Don't Shoot" during a protest after a grand jury had decided not to indict Ferguson, Mo., police officer Darren Wilson in the fatal shooting of Michael Brown, an unarmed black 18-year-old, in San Francisco, Monday, Nov. 24, 2014.

OAKLAND, Calif. — Hundreds of protesters marched through downtown San Francisco streets packed with Black Friday shoppers to protest a grand jury decision in Ferguson, Missouri.

Some in the crowd used hammers to smash the windows of stores in the city's touristy Union Square, sending scared shoppers huddled inside the shops, KGO-TV reported.

The crowd marched through the heart of the city's shopping district and arrived at Union Square, where police stopped them from disrupting the lighting of a Christmas tree in the popular area.

Some activists screamed at police, while others threw bottles and other objects at the officers, the San Francisco Chronicle reported.

The crowd then went to the Mission District, with at least two dozen police vehicles and motorcycles following closely behind.

San Francisco police did not immediately return calls seeking comment.

Earlier Friday, another group of protesters chained themselves to trains in Oakland and temporarily interrupted Bay Area Rapid Transit service from Oakland to San Francisco.

Police arrested 14 of 25 people who chained themselves and shut down the West Oakland BART station, Bay Area Rapid Transit system spokeswoman Alicia Trost said. Demonstrations have persisted in Oakland and San Francisco since a grand jury on Monday declined to indict Ferguson Officer Darren Wilson, who is white, in the Aug. 9 killing of Michael Brown, who was black.

About 125 protesters wearing T-shirts reading "Black Lives Matter" gathered at the BART station and interrupted service for about two hours until police cleared the station and service restarted, Trost said.

Authorities have arrested 181 protesters in Oakland, and there could be more after officers review video and pictures of the demonstrations, Oakland police spokeswoman Johnna Watson said.

Since Monday, some protesters in Oakland have smashed the windows of businesses, blocked freeways, sprayed graffiti and set trash cans on fire. Protests in San Francisco had remained peaceful.

Groups nationwide are protesting on Friday with an economic boycott to further draw attention to their anger over the grand jury's decision. A large protest against spending money on Black Friday was slated to start in West Oakland and end at a Wal-Mart store several miles away.

In Sacramento, five people were arrested Friday night at Arden Fair mall for failing to disperse, the Sacramento Bee reported.

In Los Angeles, small groups of protesters took to the streets downtown and in Beverly Hills, causing some traffic disruptions. Police said eight people were arrested.

Carrying signs that read "Hands up. Don't shop!" ''No Justice. No Profits," and "Black Lives Matter," a group of about 60 ?demonstrators gathered? ?Friday afternoon ?outside one of the mall's entrance?s?, while a police helicopter circled overhead. When protesters moved and blocked an intersection at the mall's main entrance on Arden Way, police told them to disperse. When they didn't, the arrests were made.