A little before 6 p.m. on Wednesday night, a teacupful of Occupy protesters (or not) "wearing black masks" worked their way into an empty building at 535 Castro Street to temporarily occupy the building.

According to the Chronicle, "About half of the crowd stayed outside the two-story building while about as many police officers gathered across the street. Police stormed the building at about 6:50 p.m. Nearly an hour later, they arrested 20 people inside the building and marched them into a waiting police van."

Riot police, clomping, tear gas (?), and lots of shouting ensued. Nothing that any regular Castro resident hasn't seen during Halloween or more critical protests. Occupiers also hung an arguably classist sign reading "Gentrification = Assimilation" (and one bystander even sent your tireless editor this cranky tweet.

The evening's wisp of a protest was planned to coincide with World Homeless Action Day, a day that "aimed to draw attention to the needs of homeless people around the globe."

Update: By about 8 p.m. the scene had degenerated into a gaggle of protesters, about 20 or 30 in all, occupying the parklet outside Dancing Pig BBQ (544 Castro) across the street from the building they attempted to occupy. There appeared to be a few homeless people who had been part of the march who were being fed a hot meal as part of the sit-in. SFPD officers, in riot helmets, closed the section of Castro between 18th and 19th to all through traffic except Muni busses, for no clear reason. We witnessed at least one protester in Walgreens with blood on the back of his head, shopping for bandages. The businesses along that stretch of Castro seemed annoyed at the ceasing of foot traffic up the block as police directed pedestrians to loop around on side streets. In any event, there were no black masks on those who remained.

Meanwhile, simultaneously in Oakland, there was a ceremony to celebrate the one-year anniversary of Occupy Oakland at which 25-year-old Marine veteran Scott Olsen, injured in last October's melee, spoke to the crowd, saying that all the assembled wanted to do was "bring people out and rekindle some of those friendships and relationships" formed last year.

Update II: Something calling itself Homes Not Jails says they, not Occupy, took over ("took over") the Castro last night. However, we imagine the two groups are not mutually exclusive.