This amateur video, from December 27, 2009, shows a security official open fire on protesters in Teheran, despite repeated Iranian claims that security forces are not armed with guns. The video also shows the crowd rush to chase after the gunman, rather than scattering as may have been expected. Iranian security forces intensified their crackdown on anti-government supporters last week, limiting the movement of top opposition leaders and arresting their relatives. The clashes were the worst since the aftermath of June's disputed presidential election. In outbursts of fury rarely seen in past street confrontations, protesters burned squad cars and motorcycles belonging to security forces who had opened fire on the crowds, according to witness accounts, opposition Web sites and amateur videos posted on the Web. Independent confirmation of casualties was virtually impossible because of state restrictions on media coverage. Britain, France, Germany and the US criticized Iran's violent response to the protests. On Monday, US President Barack Obama praised "the courage and the conviction of the Iranian people" while condemning Iran's Islamic government for attacking demonstrators with "the iron fist of brutality."