Car died after short stop

[theluckyexplorer]

Hi guys, I think I'll need help with this one. Something that has never occurred to me: the car just died inexplicably! I had just finished a 90km journey and was about to park. I needed to wait for a gate to be opened, something like 2min so I figured I'd switch the car off.
I then went on to turn it on again - waited for the glowplug light to estinguish, tried to start and... I heard a small beep and then everything just died. I tried again and again, but it hasn't given signs of life!

Any idea on what could it be? I am mindblown to say the least