Hi and Welcome. My Name is ***** ***** I look forward to assisting you today with your question.
I'm really sorry about your Mac. Your only hope is iCloud's Find My Mac option. If this option was enabled before it was stolen, then you will be able to remotely wipe and lock it down. You can do this from any computer or even from your phone.
On your current computer, open internet browser and go to www.icloud.com
Click Find iPhone (yes iPhone). Then it will find and list all the devices registered on iCloud. Under All Devices, click your Mac. Then click Erase it and it will be erased the moment your Mac connect to internet.
This is your only option to erase it. Refer this article --> https://support.apple.com/kb/ph2701?locale=en_US
I would also recommend you to change all your passwords associated with your Mac, like your email password, Apple ID password, websites passwords etc. Change all passwords. If you would like me to help you with that, please let me know and I will help you to change your passwords.
I know you are looking for a direct solution to this problem, but this is your only options left. If you are not satisfied with my service, please don't rate me bad or poor. You don't have to rate anything if you are not satisfied.
If you have any questions, please feel free to ask.