Invalid Hacked account and stole all my hats.

Hello , today i was playing tf2 and suddenly , some guy wrote me from my steam friends. He said that in steam forum's there are topic about me and that i should go and check. Yea i went to check it and then my steam wrote that my account is logged in somewhere else . When i restarted and change my pass , all my hats where gone.
Picture of Chat.

http://www.part.lt/img/4b2640a9f0529fc5a2e6decf35f8de81607.png

And the picture that my acc was logged in other pc.

http://www.part.lt/img/4210a6624ef8638ded3f4fba1caaca20319.png

His Name Is DarkSlayer and i saw on his profile that im not the first one that he stole items. Other guy wrote same thing about Topin in steam forum . So if you can please help.

http://steamcommunity.com/id/DarkSlayerDT/ His Steam ID.

http://www.part.lt/img/9c69a71cb326fe563ea3221031bb8b5f62.png Inventory History.

http://www.part.lt/img/63d382f794761cdbb31c9600cf69b150763.png Yestanuki's channel

Invalid report. Please post a new topic in the correct format.