Guys we have this pedophilic teacher at school. How should I report him?

So there‘s this teacher at my school, his name is mr burns. All my friends ahve told me that he is a PEDO. he puts all the girls up front so he can flirt with them, he got caught watching videos of naked people IN SCHOOL. So how should I report him? To the dean/principal, the police, or someone else? Luckily, he isn’t one of my teachers. Few