"you are dead."

[biscuitpureonly 0]

just happened to me. i was alone in my server, on the military base to the sw of the map. i was climbing to one of the watch post to scout for z's and "you are dead." as my character reached the top of the post.

[Judopunch 523]

Desync or lag, you fell through the floor. Old bug is old.

[Zervox 14]

I've seen this happen to a couple of friends of mine out in open fields lately as well, there is however no kill logs in ADM to confirm environment has killed a player only if a player has killed another one.

Also been together with 2 others, everyone was sitting out in the fields, then suddenly one of us collapses and he gets you are dead message, both me and the other person was fine.

there were about 6 others on the server, but we just sat still out in the fields and nothing happened to us so it most definitely wasn't a player kill, there were no kill message in ADM log(just to confirm not a player kill).

I suspect there is something more than just lag or desync in some of these cases going on, the body was also at the exact same spot he was on his screen and the same spot we were seeing him. 

[twr 43]

desync bro. good ole dayz got the best of you