South Korea's president declares, then lifts, martial law

South Korea's president has sent shockwaves through his country by trying to impose martial law in the middle of the night. The decision was met with disbelief in the people in the streets - who thought perhaps the notification was meant to say North Korea. The ordeal didn't last long, and was lifted about six hours later. But it's caused a political storm - and now there's calls for the president's impeachment. CNN's Mike Valerio is in Seoul where protests are taking place, he spoke to Lisa Owen.