"We're here to put pressure on the G20 to ultimately abolish global capitalism," said a 24-year-old man from Delaware, who declined to give his name.
Protesters wore bandannas and goggles and held aloft a large black sign declaring "No hope in capitalism" and another saying "Kick Capitalism While It Is Down."
Police in riot gear used pepper gas and ear splittingly loud sirens to disperse them.
It is interesting to compare the Pittsburgh mob with the several hundred thousand who marched in Washington DC recently.
The DC demonstration was orderly. They were mostly Republicans, Conservatives and Independents. Many of them were Senior Citizens, yet Nancy Pelosi referred them as an unorganized mob.
Wonder what she will have to say about the real mob of about 2,000 leftists in Pittsburgh that wreaked havoc smashing store windows requiring the police to use pepper gas and loud sirens.
More about the violent Pittsburgh demonstration story here.