is ctrl+win a kill switch for i3?

I on occasion accidentally hit ctrl+win and it seems to kill i3. screen goes black, and no key combination I have tried gets the screen to return. I have programmed my lock screen to be a completely different key combination so I know it is not the lock screen, although I have tried my password and that still doesnt work. Now when I press the power button, the screen comes back and i3 has been killed and shutdown is being initiated. I looked through my i3 config file and found no keybinding using ctrl+win. Any ideas? It's on arch btw