Caught my 13 YO sexting

Okay so my son just turn 13. I’ve had the birds and bees talk with him a few times. I’ve talk to him about body safety and picture safety. We are pretty open with things as I’m a single mom. I know he has “discovered” himself because I accidentally walked in on him one day. So of course it was awkward but I talk to him about it. Letting him know it was normal and that as long as he does it in private, don’t over do it and is clean about it then that’s fine. I mean what else was I suppose to say? Anyway…fast forward to last Saturday, I discovered he had a “crush”. Prior to this he never talked about girls and would get all weird if anyone asked him about girls. So he told me about it, and I’m like that’s fine. They just talk on the phone, not like they see each other anyway as they don’t go to the same school. It’s my nieces best friend and they’ve met maybe once or twice in person. Long story short, I went through his phone and discovered that they were talking about having phone sex. He deleted the messages but I looked in the recently deleted. I guess they both touched themselves while on the phone and they talked about how cool and it amazing it was. Now I’ve taken his phone away and talked to him about it. I told him he was too young to be talking like that and that although masterbation is normal, it’s something you do ALONE and not with anyone else. I also told him he shouldnt be telling everyone his business (I seen him tell his friends about it). It made my stomach turn because these kids are only 12-13 years old! I’m unsure about what I should do next? Do I contact the girls parents? I mean if it was my daughter I would want to know. I just think they’re way too young to be doing this kinda stuff and never thought I would be dealing with this so early on. Please advise me on what to do here. Is this normal?? Should I get him in therapy?? I don’t want him to end up one of those horn dog guys that us women hate :weary:.