The full facts on this one will have to emerge, but you can see how such incidents happen...
Last month, I was treated to the spectacle of a pair of disinterested baggage-handlers unloading a WJ 736 at YYZ. Yes, it was late and VERY hot, but there were the usual signs of sloppy work: bags dropping off the conveyor / items being thrown into the carts etc etc etc. The baggage carts departed just as a final item came out of the hold. Even with the sign-language of distance, the FO, doing his pre-flight walk-round, clearly indicated to the handler to take the extra bag and the latter refused. A lot of pointing and hand-waving followed, ending with a jab in the chest from the handler(!) Legally, that equates to assault. As SLF in the terminal above, I have no idea what happened thereafter, but either way, I doubt the FO could have been in the best frame of mind to fly.