A group of Occupy Oakland demonstrators march through Downtown Oakland during an attempt to occupy a building in Oakland, California January 28, 2012. Police fired tear gas at hundreds of Occupy Oakland protesters who tried to take over a shuttered convention center on Saturday, arresting 19 people in the latest clash between anti-Wall Street activists and authorities in the California city. REUTERS/Stephen Lam (UNITED STATES - Tags: CIVIL UNREST POLITICS BUSINESS TPX IMAGES OF THE DAY)