He was with her when she went missing and was seen on camera with her. By the sounds of it, they had been friends since 2016. I guess not that long. Can't say if they ever dated or not, but I get the feeling that he wanted to be more than friends and she didn't feel the same. The usual. Guy can't handle rejection so kills the woman. That's what I'm assuming at least.
ETA: This is the thread on her Mom's Facebook that discusses what I'm talking about for reference:
https://m.facebook.com/story.php?sto...composer=false