After marshmallow phone is locked up

[douga54]

After initiating the Marshmallow update my HTC One (M8) started to reboot but stopped at the red Verizon bootup screen. Now I can't power it off. I think there is a combination of volume and power key to do this but I don't know for sure. Can anyone help?

 

[today]

If I'm not mistaken you can just hold down the power button for at least 10 seconds.

 

[saltire]

If that doesn't work, press and hold power + vol up should force a restart.