15 y/o son has been talking to a woman in her 30s..

So my 21 year old daughter is back from college and she took her brother's phone while he was asleep because hers was dead and she couldn't find her changer. She came to me about an hour ago, shook me until I woke up, and told me "I think you need to see this."

This is what she was talking about.. He's using some texting app to message her and when I would exit, I couldn't find it. So I assume he's hiding it because I know you can hide apps but I don't know how to access them. My son is gonna be in a world of trouble when I get my hands on him and I'm trying my hardest to find more information on this woman but I can't! The only thing I've found so far from scrolling up is that she turned 33 on January 5th. And I'm scared he won't tell me the truth so I can go to the police. I'm actually crying as I type this because I failed to protect my kid from a predator. This is a mom's worst nightmare. Hell.

Heres the update