The party was already in full swing at 8:30 p.m. tonight, with skaters careening down Dolores Street, some wiping out at 19th, others continuing down the hill toward 18th Street as more than 100 people looked on.

“Don’t cross,” advised one onlooker as a skater whooshed north on Dolores. Many of the onlookers who lined the street held skateboards at their sides; others watched with a beer in hand.

Except for a few cars that managed to get through, most of Dolores was blocked off from 20th to 18th Streets. It was the third year in a row that skaters organized a hill-bomb event at Dolores Park. At last year’s fete, skaters clashed with police.

The party started earlier in the evening.

Dolores Street is on ??? #skateboard #dolorespark

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Ah, yes, a planned event.

At 10 p.m. Thursday, police had not yet arrived on the scene and for the most part, the crowd was just having a good time.

The crowd at Dolores Street.