What can happen when an adult hits a minor?

This really tall and big Samoan dude keeps picking on me. Slapping the back of my head hard every single time I see him. It's been happening since last week. And every time I see him he licks his hand and slaps my head. He even told me Ima slap you every single time I see you. If I call the cops what would happen. Do I need any evidence for this claim? I'm getting annoyed as I'm only 15 and he's 30 and over 6 ft tall. And I'm only 5"3. The reason was he caught me ditching school and hated me ever since. Even tho my dad already dealed with me at home. And still he slaps me. I'm just scared if I call the cops Ima get chased after by his boys. Cause he is very well known in our area. And im afraid Ima get mobbed. Idk what to do. He's on his probation too so will that get him in more trouble?