How Beijing might respond to escalating Hong Kong violence

Police in Hong Kong have tightened their siege on the campus of the Polytechnic University, where hundreds of protesters are trapped inside. It’s the latest bout of violence in nearly six months of demonstrations -- one China is warning it won't let go too far. Nick Schifrin reports and talks to Kurt Tong, former U.S. consul general to Hong Kong, about the protesters’ strategy and U.S. response.