Or more easily from one of these if the driver had a simple Tyvek suit and mask on:
But more than likely, it was launched by rocket, or mortar. Mortar's are more dangerous if the canister breaks when fired. But the deployment of Sarin is as easy as putting it in a CS gas canister, driving through a neighborhood, pulling the pin and throwing the canister as you haul butt out of the area.
There are other chemicals that are more dangerous to the people deploying it, and cannot be as easily deployed; Phosgene for instance, which is what Saddam Hussein used against the Kurds in northern Iraq.