It’s more likely GCC HUMINT on the ground observing the government helicopters dropping the chlorine cylinder bombs. You know GCC commandos are all over the ME right?
Who cleaned ISIS out of IRAQ?? It wasn’t US troops.
Anyway there are lots of youtube videos of Syrian government helicopters dropping barrel bombs.
Remember The Syrian rebels don’t have aircraft.
...and there are even more You Tube videos of UFO's
almost every journalist who has attempted to cover Syria has been kidnapped and tortured , beheaded or missing. Most reliable source is the word of "syrian rebels"