There are numerous reports of random, unexplained death throughout this site (0003427, 0004643, 0005598, 0007797, 0007969), so my suggestion is hopefully a simple one: provide us with some kind of indication as to what caused our death on the "Your are dead" screen.

Examples:

"You died from - zombie damage"
"You died from - fall damage"
"You died from - Mosin damage"
"You died from - starvation"
"You died from - heart attack"
"You died from - auto-erotic asphyxiation"

etc.

Better still (if doable) would be some kind of log of the last 3-5 types of damage you took before you died:

  You took zombie damage.
  You took zombie damage.
  You took Mosin damage.
  You are dead.

In the example above, it would be fairly clear to the player that they were sniped while fighting a zombie - thus saving one extra bug report about an insta-kill from a zombie. Reports of true random deaths would be much more clear because we could show exactly what we died from (ie. I died from falling damage just hanging out the 2nd floor of a building).

For the alpha phase, I think this would go a long way in helping us provide more meaningful feedback. This message could later be removed if people feel it ruins any kind of immersion in the game.