Video: Video appears to shows Syria chemical attack victims The video may lead to more calls for deeper US involvement in Syria's bitter civil war. Earlier Defense Secretary Chuck Hagel says the US intelligence community believes the Syrian government has used sarin gas on a small scale against rebels trying to overthrow the government of Bashar al-Assad. While President Barack Obama has declared that Syrian use of chemical weapons would be a game-changer, his administration made clear it would move carefully - mindful of the lessons of the start of the Iraq war 10 years ago. The White House said the evaluation that Syria probably used chemical weapons was based in part on physiological samples, but a White House official declined to say what kind of evidence it had, such as soil samples or blood or hair from victims. The scale of the sarin use appeared limited, with one US intelligence official noting that nobody was "seeing any mass casualties" from any Syrian chemical weapons use.