Exclamation My phone just die and it is not responding.

Today my phone was working fine and it was working fine all the time. I have 4.4.4 Android unlocked and not rooted (it was rooted, but when i updated to 4.4.4 the root was gone and i didnt put it on). It was in my pocket and when i got home i wanted to start the sceen and it dosent react to anything. I tryed charging it (thinking the battery died, not nothing on the screen), try pushing all the buttons (3 buttons in the same time) nothing again. it is so strange!? what i can do? i have connected to my computer, but the com is not detecting it. and the screen dont react at all. this is so strange!?!?!?