Motorola Moto G (2014) — Moto G 2nd Gen black screen, but still can hear volume buttons "beeps".

Hello AndroidPIT,
Today, when waking up (with the cellphone alarm), my brother as usual took his Moto G and clicked the power button (in order to turn on the screen, to turn off the alarm), but the screen didn't turn on, but the alarm was still ringing.
I don't know exactly what is the version of the cellphone, but I strongly believe it's lollipop.
Has anyone else experienced such thing? I tried to enter the boot menu (or something...) by holding the Power Button and the Volume Down button, but it wont work. The cellphone is like 1 year old, I don't believe it's already dead...
Thank you very much!