Why did my chromebook shut down randomly?

While I was using my Chromebook, I was typing and then it shut down for no reason and for some reason, I wasn't pressing the power button nor the power button on the menu of the system where it shows the time. Can someone explain to me how can this happen? (Btw, it is a school Chromebook. also, I did not have apps open and I was just using Google Chrome with not too many tabs like only 3 tabs open, and still turns on with no problem like nothing ever happened.)