In southern Brazil last week, around 100 cycling activists were mowed down by an angry driver. Associated Press reports: "Cyclists in the Critical Mass ride tell the Folha de S. Paulo newspaper that the man argued with some riders, who had taken over all lanes of the street on Friday."

No bike riders died during the incident.

According to Deadspin, the suspect is motorist Richard Neis, who "tailed the Critical Mass bikers for some distance in his black VW Golf before gunning the engine and plowing into them. Neis later ditched his car but decided to give himself up to authorities."

The video, which you can view below, shows a peaceful protest in progress interrupted by a car accelerating through the riders, "leaving the injured on the street screaming as fellow cyclists administered first aid." It's pretty brutal. Watch it if you must.

Fortunately, bike-heavy San Francisco has yet to see a similarly venomous display from a terse driver during our end-of-month Critical Mass ride. However, back in June, a motorist went on a hit-and-run rampage targeting cyclists in the Mission and Potrero Hill.

Video below.