How do you discipline children

I have a five year old and when we visit grandparents house he will get upset and throw things and lately he will throw things at them they are older and he threw something at his grandmother's eye and it hurt so much she broke down crying

I'm not sure what to do?

I am his mother and I try raise him best I could and my family misses me asks me to come visit when we arrived he broke family members coffee machine it was old, by touching a switch after I told him do not touch anything on this counter, next they had installed a expensive door $5,000+ and he kept messing with the door nob slamming the door we were all frightened he would break it we told him to stop but would continue.