I occasionally lurk on 4chan (in particular /sg/ since they aggregate lots of data regarding the Syrian civil war) and I witnessed this one particular event first hand. Now I understand that this is not a verifiable source but I found this as well, that sums-up the whole thing:
http://2static.fjcdn.com/pictures/4chan+pol+sg+orders+an+air...I don't think you will be able to find anything better than that to "prove" it happened.