Screen won't turn on, flashlight won't turn off.. d'fuq?

My boyfriend's iPhone is pretty old and pretty well-worn. We were in a sauna when his phone started really glitching out.. The flashlight wouldn't turn off at first, the flashlight button on the screen went grey, as if there was no flashlight connected or something.

Then the screen went black after a few minutes of us trying to fix that and it's been that way for the entire night.. The phone will buzz when connected to charge, and made a "tap" noise recently as he was trying to mess with it, but no real changes..

Trying to turn it on, charge it, hard reset, even smacking the camera on a corner as one person on this site suggested, doesn't work.

HALP.