According to the call-ins today from downtown, it seems that tonite's PPRC march was around a thousand people, and that it ended up coming back to Pioneer Square. A little after 7 o'clock the march left the square, started winding around every which way and ended up going the wrong way up Broadway. The cops seemed to be trying to mobilize to stop it, and they just kept bringing more and more cops as the crowd played cat and mouse with them and sat down in the intersection of SW 4th and Stark.
At this point more cops closed in, horse cops, bike cops, robocops, "every kind of cop imaginable"...The ice cream truck was brought out to send messages to disperse to the crowd, pepperspray began to fly and people started to be arrested.
Eventually, around 8 o'clock or so, the Morrison Bridge was shut down by kops and the entire area west of the bridge was filled with kops and vehicles horses bikes and motorcycles, "every kind of kop imaginable", closing many streets... The situation seemed to have deescelated by around quarter after 8. Not sure how many have been arrested.