I have a 3.5-year-old DCK who hits more than once a day. Just starting out with him, so want to get it under control now. I think the causes vary somewhat. Sometimes it's because of frustration of not getting a toy from another child. But then sometimes he'll just walk past and hit or push another child. 50-50 on whether I'm right there or not when it happens (sometimes it seems to be attention since I'm right there and he looks at me for the reaction, but sometimes not). What to do?