Quinn McCormic, 25, of Boston, Mass., was arrested on Friday and appeared in a Toronto court Monday to face four charges.
McCormic, an architect, consented to his extradition and was arrested when he arrived at Pearson International Airport, police said.
It's alleged that McCormic threw an object at the window of a Winners store (at College Street and Yonge Street) and that he also threw an object through a window at a CIBC bank (at College Street and Bay Street.)
They also allege that he threw an object through a window of the Toronto Police Museum (at 40 College Street) and estimate the total damage at more than $125,000.
McCormic is charged with three counts of mischief over $5,000 and disguise with intent.
Dozens of protesters — many wearing disguises — went on a window-smashing rampage through downtown Toronto during the international summit in June 2010. Damage included police vehicles that were vandalized and set on fire during the mayhem.
More than 1,100 people were taken into custody that weekend in one of the largest mass arrests in Canadian history, although most were released without charges.
However, more than 40 people have been successfully prosecuted for their parts in the rampage.
Police say suspects in the violence included five Americans who returned across the border after the summit and that with McCormic's arrest, four have now been apprehended.
Dane Rossman, of Tucson, Ariz., and Richard Morano of Pennsylvania, are in custody pending extradition and Joel Bitar, of New York City, was arrested earlier this month.
Police allege Bitar is the masked man who was seen hitting windows in the financial district with a pick axe, and accuse him of causing about $400,000 in damage.
He faces 26 charges including mischief over $5,000 and assaulting a police officer.
Police say they are seeking a fifth person, Kevin Chianella of Pennsylvania, in connection with 50 Criminal Code offences for damage estimated to be in excess of $300,000.
"I believe these Americans came to Canada specifically for this criminal purpose," said Det. Sgt. Gary Giroux, who leads the G20 Investigative Team responsible for identifying and prosecuting those who committed crimes at the summit.
Giroux praised United States Marshals and the Federal Bureau of Investigation for their assistance.
"The process of preparing the necessary documents can be very time-consuming. They go from the Crown Office here, to the Department of Justice in Ottawa and, then, the American authorities for final approval. But we're persistent and we will hold people accountable," he said.
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