My 4 year old is calling himself stupid and hitting himself when he's upset

Im not sure this is where to post this, if not just let me know. I have a four year old who keeps hitting himself and saying things like "I'm stupid" "im the stupidest person in the world" and hitting himself. He goes to daycare, and I'm thinking that he saw someone else do that and get attention for it. I don't know how to curb the behavior. I tried ignoring it but it's gone on for a few weeks. Any advice? via /r/Parenting https://ift.tt/36LGA8v