Behavior chart

Attempted today to use behavior chart with Kindergarten student who's been so difficult in the art room.  As he's been removed from every classroom for his behavior, his parents have had to either take him home or stay with him in school.  His mother was here with him today and before they came to art I showed both of them the behavior chart that I created for him.  If he comes into the art room without running he gets a sticker on the chart, stays in his seat for the whole period gets a sticker, shares art materials at his table and works well with others, etc. he'll get a sticker at the end of the class.  He started off well-came into the room without running and sat in his seat. But then he started calling out, snatching materials from other students at his table and wanting to get up and sit in other people's seats. His mother was in the hallway with his classroom teacher so he was sent to be with her.

I'll have to give him a sticker for at least coming into the room and sitting in his seat. His mother is with him now but seems so unattached like she didn't give birth to this child.  How do kids become like this?  His behavior wasn't bad to this extreme until recently.  Something going on.  Wish I was a camera looking into their household activities.  Or maybe not.