stripped torx

For the last couple of days I have been trying to work these torx screws off so I can add some mirror mounts. Top one was stripped so I tried an extractor bit with no luck. The head of the torx snapped off on the last try. How can I get the rest of it out? Is there a way to access the back half...

I stripped my seat belt torx bolt and was seeing if anyone else had that problem and how they went about removing it.