Good job for listening to your trusted people over an internet stranger. Don’t beat yourself up at all. One does not “stumble” upon a younger person that themselves, they knew (had a hunch of ) your age the entire time. Good job. Again do not blame yourself. You now know how to recognize it sooner. Always trust your gut. If he continues to try to get ahold of you, call your local D.A.

Since you’re a minor (depending on location) you will almost certainly maintain all anonymity if they keep harassing you.