I'd like to say thank you for your advices and replies! It's been more than helpful and comforting to read all of those advices. Thanks sarahd80 for the Triple P (PPP) recommendation, I googled it up and found one PPP group that will be running in my area. Won't be held until late April, but I'd be more than happy to participate
I've had such a long (and emotional) day today (been running around everywhere, and on top of that my job hunting doesn't go as smooth as expected, and been stressing it out for weeks ), so I have not had a chance to ask DS properly (firmly but kindly) how he said that gun word to Mrs A. He finally demonstrated it to me when he calmed down whilst doing some arts and crafts. So it wasn't in a violent or threatening way, but it was still inappropriate no matter how you say it. The way he showed me was he was pretending to be speaking in an animated voice to a walkie-talkie and pretended to say it to the other end that he needed some 'help' here and needed the 'gun' (i assume he was sitting at the 'time out' corner because he said he was in that mat where he said they'd put a boy/girl who's noisy/loud there, i think that happened during the story time he might have talked out loud in silly voice) and prior to that he was also having problems with Mrs A in regards to the school work thing he refused to finish (great, that just completes his view on Mrs A today). He was basically trying to be a smart *ss pretending to have a power (gun) to show it off to his teacher - I don't have any idea what young boys are thinking about!
I know I will have to speak to Mrs A when she gets back next week (her teaching days), but tomorrow I'd probably ask Mrs B at the end of the class so that she's aware as well... she may already be as it's already in the school book anyway.. which is probably gonna go up to the principal? *Gulps*