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The city of Pittsburgh is not only hosting world leaders for the G20 summit. Thousands of protesters are using the event and the media covering it as a way to get their message out. The summit is also an attractive target for people who hope to disrupt the meeting.
The city of Pittsburgh looks and feels like a fortress. Streets lined with businesses and usually bustling with people are now boarded and empty, as thousands of law enforcement officials secure the area around the city's convention center, where the G20 leaders are meeting.
Not far away is the closest, authorized protest allowed by the city of Pittsburgh during the summit.
Tianlun Jian helped organize it to draw attention to the persecution of members of the Falun Gong spiritual movement in China.
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"Once they saw these pictures, the authority who gave the permit was actually moved to tears, and she said, 'How can this happen to humankind?' And she also said, 'you guys are righteous, you guys are upright, you are doing something we want to do,'" Tianlun Jian said.
Most groups that have permission to protest are media savvy and know how the news agencies that have descended on Pittsburgh can help spread the word about their causes.
Groups not authorized to protest are also trying to profit from the media presence.
Thousands of protesters loosely affiliated with what's called the Pittsburgh G20 Resistance Project gathered at Arsenal Park, about two miles from the convention center.
Albert Pertrarca decided to join the protest despite warnings from police that the gathering was unlawful.
"We are outraged that a democratic administration has essentially imposed a police state on the city of Pittsburgh," he said.
The gathering was originally peaceful, with a circus-like atmosphere, but it turned violent as protesters challenged police trying to break up the crowd. Protesters hurled rocks and rolled trash dumpsters into the path of law enforcement vehicles. Police used tear gas and pepper spray to counter the crowds. At least a dozen people were arrested.
There are more than 4,000 law enforcement officers in and around the city of Pittsburgh. None of the violent protests has reached the established security perimeter near the Convention Center.