My ex is using a burner app to annoy me?

I'm staying quiet, I'm not replying or even letting him know I'm even acknowledging his attempts to get my attention. I've found out that he updated his profile to "in a relationship" but there has been no trace of this so called girl. I am trying to move on, I'm talking to other people and I've downloaded tinder. Which he is on also, if he's on there... there's no way he would be in a relationship. So I get a text saying;
"Just informing you for future reference to stay away from my man. I don't have anything against you, I just do not want drama"
I haven't contacted him, I've been ignoring him completely. What's his deal, is he going crazy?