To do what this fella has done would take me 2 minutes. This fellow has simply redirected his site to yours as webzcas has suggested. If you scroll around the page your domain is everywhere. The person is positioning using your site rank high then whammo a partial change.
This could also still potentially harm your site. For now I would keep a close I on this person. I would for sure contact this person, server ect… its a magician trick. greek39