I'm really really sorry for your loss, 13BTC is a very big amount. hope you can let it go and face the future as usual again.
How could this happen? very sad. You have lost 13 btc in an instant. Whoever takes it, he will not want to return it. It will be a lesson for all of us to always be careful. It's important to keep your password and private key in crypto coins. Whatever it is, it is information that should not be shared with anyone.