The San Francisco Chronicle has a timeline of the riots. Here are a couple of the key timeline entries:
1:20 p.m. Tensions rising: Far-left demonstrators wearing black masks and body armor have joined the crowds gathered at Civic Center Park.
Tensions at the park have been on the rise as police in riot gear abandoned their post along a concrete barricade within the park separating the right-wing demonstrators and the counter protesters.
Police are now surrounding the perimeter of the park to deal with masses of counterprotesters who are trying to get in.
1:35 p.m. Hundreds break through: Berkeley police in riot gear stepped aside as hundreds of counterprotesters jumped the barriers around Civic Center park and flooded the place. All very peaceful. One protester said that was “too easy.” Fighting broke out and pepper-spray and tear gas filled the air as hundreds of men and women clad in black moved through the park.