Phone randomly shut off and won't turn back on

[Andysan420]

I have 2 phones that I use; One of my phones just died and wont turn on after watching some videos, even though it still had some power left. The other one was turned off overnight and then the next day when I turned my phone on, it immediately died after. What do I do?

 

[Saga Lout]

If the used the same charger, maybe it wasn't working properly and both are dead flat.