IPad stuck in Face time call

I was on the phone with my friend earlier and click on the PIP screen. When I clicked on it the screen was in the corner and just disappeared so now my iPad is stuck on the "this FaceTime call is in picture in picture" screen. I can't power off, I can't go back to my home screen, I turned off my internet and have airplane mode on and it still says I'm in the face time call, siri won't work to power off, and when I try to turn it off I just hear the turn off sound but it doesn't turn off. What do I do because I can't do anything from here but wait till my iPad dies which will be forever because it is on 100%...