Lashing out when scared

[Angel]

As I've mentioned before, K is fairly reserved and has major stranger anxiety issues atm. In the last couple of months though I've noticed that when he feels threatened he has a tendency to lash out. When we go out he is happy to play away from DH & I and enjoys watching other people but if someone he's not familiar with gets too close to him he shuts down - he'll just stay very still, doesn't make a sound and stares at the ground. I don't push him or try to force him to do anything he doesn't want to but I do keep chatting to him and try to make him feel safe & comfortable so that he can join in if he wants.

A while ago we were at the markets and K was happily playing with some gravel on the grassy area about 3m away from where I was standing. 2 old ladies came and stood between us and were smiling at him. I started to walk around them so K could still see me and as I was doing so K held up a piece of gravel to show to the ladies. He does this with a lot of things when he wants you to tell him what it is but it looks like he's offering it to you, which is what one of the ladies must have thought as she walked up close to him and tried to take the little stone from him. When K saw how close she was getting he panicked, threw the gravel at the lady and then started screaming in fear. I apologised to the lady and told her he gets a bit shy when people get too close and then I calmed K down and told him that I understood that he got scared but it's still not very nice to throw things at people and the lady just wanted to say hello to him. I didn't make a big deal out of it because I didn't want K to think he was in trouble as I know he was just scared and didn't do it to be nasty or anything.

More recently, again at the markets, K was standing near two 2 year olds and was watching them play (he's been introduced to them before) and he was fine, happy just to watch, until they ran up to him. Obviously they were just curious about him and wanted to play with him too but, as kids do, they got right up close to him. K did his staring at the ground thing until one of them got within a couple of centimetres of him and he panicked and he pushed the other little boy in the chest. Straight away, without even thinking, I said 'uh uh darling, be gentle, we don't push people. X just wants to be friends and play with you.'

I'm not sure what to do. I don't know if I'm handling these situations in the best way or if I might be making things worse for him... I don't want him to think it's okay to lash out like that but at the same time I don't want K to think he's getting into trouble for being scared.