Normal?

My son is 19 months and he’s been smacking himself and others, biting people, and slamming his head down on the floor or head butting people really hard. I have no clue why or where he picked this up from... I refuse to spank him for hitting I think that’s a little ironic so what other things can I do? I do the firm grab his hands and say “no that hurts” or “no we don’t do that” or simply just “no” and “stop”. Nothing is working and he’s constantly doing it.