Please answer! creeper advice!!!?

okay so this is sorta weird but anyway im 13 and this kid who is 19 started talking to me and my bestfriend and he was a total creeper! but it was kind of funny but not anymore because he keeps sending me text messages saying he wants to **** me and also sending not appropriate pictures if you know what i mean.. and so i just dont text him back obvisouly and then at the mall me and my bff saw him and i was like ewh lets walk the other way!! and he was like EMILIE EMILIE HEY and came up and smacked my , and i was just like woah wth! He use to go to my school but now hes graduated and he is really started to creep me out, at first i thought he was like kidding kind of, but now im not so sure!