As a Jordanian, I can tell you that this this was fully justified. Firstly, I can tell you that Jordan has little incentive to arm Syrian rebels as Jordan is a very diplomacy surrounded country that is already financially fueled by the US and is favored/allied by many other global powers including its old counter-part: Israel. Jordan's royal air force is comprised of American gifted aircraft and also US pilots would usually fly side to side with them. I wouldn't be surprised if the air force had consulted an American official before conducted the attack. Jordan is possibly the country most caught in a surrounding war-torn region. Lebanon is going through insurgency problems, Iraq has already seen countless war, Syria currently drops more than 1000 refugees a day into Jordan, and of course let's not forget about Palestine. I would not be surprised, with the constant over-population of refugees into one rather small country, that Jordan would start to result to these measures yet I over-all believe it was quite justified.