Did you encrypt your wallet with password?
Next time don't use Windows. Use Mac OS X or GNU/Linux. If you store large amount of bitcoin, you may use cold storage / paper wallet.
Was you using windows without an outbound firewall? (Windows firewall does not block Outbound connections and any undetected key-logger would send everything to the hacker without you even knowing)
the wallet had passphrase encryption. Not sure about the firewall. Kasperski and AVG were on and nether triggered. ran Malwarebytes.org scan and it did flag a bunch of stuff that the AV programs missed. Certainly learned a lesson about importance of paper wallets.
this character has posted to this community in the past. I am hopeful moderators can DOXX him and hopefully together we can shame/coerce the guy to return the coins.