Big difference from the 9/12 Tea Party.

Police threw canisters of pepper spray and smoke at marchers as US President Barack Obama and his wife, Michelle, arrived for a meeting with leaders of the world's major economies.....

Elsewhere in the city, there were reports of rocks being thrown at buses in the Bloomfield district, where the windows and ATM of one bank were damaged.....
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In the city's Lawrenceville district, about a mile from the summit venue, police deployed tear gas in order to disperse crowds after warning everyone in the area to "leave the immediate vicinity regardless of your purpose." Protestors responded by throwing bottles at the officer.

Those gathered came from a variety of groups and causes, including Code Pink – which is a female-led anti-war group - Greenpeace, and some calling themselves the G20 Resistance Project.
Source.