In my opinion, it is not achievable. If it is just over the internet. Especially if that individual is not someone who knows you in reality.
But if that person did, your life will really be at risk. Which means that you have to be extra careful of your surroundings. As soon as you find evidence that, that person knows your real identity, go straight to the police.
If it is only here. Do, what everyone said here! Have Pet, notified about this.
My advice as well as what other people will say. Be careful of the informations you give to other people. As well as what you post!