Twist on black screen of death - how to turn off in the first place so you can do the reboot

[AC Question]

My wife's S6 is on. You can call it - it rings. It is receiving text messages. The screen is totally black and non-responsive. All of the postings regarding a system reboot all say to turn it off and then hold a combination of buttons. I can't power it down with the screen non-responsive. Any suggestions for how to power it down?

 

[nahoku]

From a google search... link

 

[belodion]

Press and hold Power and Volume Down for half a minute or so. That's a simulated battery pull.

Edit: Posted same monent as above.