After a couple of hours of playing, I had acquired plenty of food and drink. Also found some bandages, a gun etc.

Suddenly, the "Your are dead" screen pops up for no reason. I was on the second floor of a building standing facing the door. There was nothing there. Just instant death for no reason.

I understand this is a bit vague and difficult to reproduce, but here it is anyway.

Edit: After reading some other tickets it has become apparent that this was caused by wearing a Gas Mask. Seems wearing a gas mask causes damage until you die.