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Some 150 protesters stranded hundreds of commuters on Monday evening as BART partially closed stations at Civic Center, Powell, Montgomery and Embarcadero from 5:15 p.m. to somewhere near 8 p.m., according to our reporters on the ground.

As commuters left work and tried to get home, they found BART entrances blocked off, trains passing their station and a small group of protesters shouting slogans against BART police and officials. “No justice, no peace. Disarm the BART po-lice,” some chanted at Civic Center.

The group remained relatively small throughout the evening, but effectively created enough commotion to stop BART. At the end of the day, the main lesson from the protest seemed to be that it takes relatively few protesters to undo BART.

“Montgomery BART station now open while Powell and Civic Center remain exit only,” tweeted a Mission Loc@l reporter at 6:30 p.m.

Often, BART officials closed off the station entrances but allowed the trains to stop and passengers to exit. Officers prevented commuters from entering the stations, leaving them stranded — at times angry and at others consigned to their fate.

“Who wants to split a cab?” asked an angry commuter at the Embarcadero station at around 7:15 p.m.

When a tourist appeared befuddled by the protesters at Embarcadero, an officer asked, laughing, “Do you want to go shop or do you want to protest?”

At other stations, such as the one at 16th Street, trains moved through without stopping.

By 5:45 p.m., BART had closed down Civic Center station and moved the protesters out, and shouts of “16th Street, 16th Street, came from the group. But instead of moving toward the 16th Street BART station, the protesters marched east on Market Street, headed for the Ferry Building.

The protest was planned after one that was scheduled for last Thursday fell apart when BART cut off cellphone service to four downtown stations. The August 11 demonstration had been planned to protest the July 3 incident in which BART police shot and killed 45-year-old transient Charles Blair Hill on the Civic Center platform.

The suspension of cellphone service prompted outrage from protesters and civil liberties groups, and over the weekend a group called Anonymous hacked a BART website and published some customers’ information. The Anonymous website also built some support for Monday’s protest. Cellphone service appeared to be unaffected during Monday’s action.

During the protests, Mission Loc@l experimented with Storify, pulling tweets from our reporters and others as well as photos and articles. We also live-streamed from Civic Center for more than an hour using Qik. Later, we tried again at Embarcadero, but you can see from the brief video that the cellphone reception there was difficult.