15 yr old son being stalked online for years.

We’ve delt with this problem for years. This all started when my son was 12 he met a girl who was the same age as him on musically. They used to talk everyday and make musicallys to each other. When my son was 13 I took his phone away because there was some suspicious text messages going on between him and this girl. The girl kept asking him where he lived, what school he goes to, what type of girls is he interested in etc. my son only answered the last one because he knows not to give out that information. When my son didn’t answer those other questions the girl got all upset saying why don’t you trust me, we’re friends, come on tell me where you live. So I drew the line and told him to block her and don’t ever talk to her again. Of course he was upset at first but then a couple months after that happened he said she kind of creeped him out. For that moment I thought she was gone for good. We went a whole year without having anything to do with this girl. My son was off all social media’s for a year (his choice). He said he never wants to run into her online again.So this year, my son decided he would get back on social media. Just Instagram not musically and my son made a new account on Instagram. Only accepting school friends and it was a private account. About to weeks later he got a message on his phone while he was eating breakfast with us. He looked down at his phone and immediately said omg it’s her. I asked who? And he said that girl that I used to talk to she found me again. She didn’t friend him, she messaged him through messaging. I don’t know how that could happen unless this girl has been searching for him for years. But he’s been off every social media for a whole year and two weeks within getting a new Instagram we receive a message from this girl. Has she still been searching him this whole time? Has she been stalking my son? I don’t know what’s going on here. I told him not to answer it and block her.We’ve all seen this girls “face” on musically but I don’t think she is who she says she is. Her account was public so we could see all her posts. All she posted was stuff about my son! How she misses him! And needs him back and has been searching for him for a year! This is absurd! I honestly don’t feel comfortable letting my son on Instagram.About two hours later he got a phone call on his phone and he answered it. He said I don’t know you who are you and then he immediately hung up and said now she’s got my number. How is this even possible? Is she a hacker or something? My son never gave out that information ever. So I don’t know what to do. Do we involve the police? I’m at lost here via /r/Parenting https://ift.tt/2rSOpe2