Will Assad use Sarin gas on his own people?

It is being reported that the Syrian military is arming it's air-to-ground missiles with deadly Sarin gas canisters. If used, thousands of Syrian civilians could be killed in a very short time.....we're talking minutes after exposure.

Obama threatened Syrian President Assad that gas attacks on civilians would not be tolerated, but what's he going to do? Once they're deployed, it's over. You have to stop a gas attack before the attack. What's the point afterward?

For the record, I oppose any, ANY interference in the Syrian situation. It's not our responsibility.