Happily my friend has updated her facebook to say all injured are out of hospital, so none too serious.
The articles seem to suggest it was an accident, in reality my friend reports an angry driver accelerating thru the mass as they set-off, they'd only been riding a few hundred metres.
Undeterred, they're gonna reclaim the streets again on Monday.
looks intentional to me - no attempt to stop. Driver removed license plates and ditched the car.
http://www.youtube.com/watch?v=ZARjUMaOfyQ&feature=player_embedded#at=137
http://www.verbicidemagazine.com/blog/tragedy-at-critical-mass-bike-ride-in-porto-alegre-brazil/1341