While playing in a full server, TORONTO 3PP ON (if i recall correctly), a player approached a building that we were in and began talking to us. He then began to describe each of our characters as well as to name one of the players in the building with us.
A fight took place, and the player in question teleported on top of the stairs (possibly desync).
video for reference
https://www.youtube.com/watch?v=UdDQraDpDaE&feature=youtu.be
It's possible to lean into walls and look trough the building, so that's how he could have seen you.
If you compare the bandwiths of players you can tage a guess which players are in your proximity, so that's how he could have found out your names.
So he could be just exploiting, but I think he was cheating and using an esp.
That he could tell your nicknames and equipment is somehow strange.
The fact that people seem to teleport in a gunfight seems to be normal... as said by biggoron, it is known that the bandwidth rises when there are other players around. And when you watch the connection symbol on the bottom right, it was RED right before the "accident". So maybe you just received the "hackers" position very late from the server (1st possibility). 2nd possibility is, that the server does somehow fail generally in telling his position. As I'm from germany, I'm watching these guys playing DayZ (http://youtu.be/FAhLb41tbZA?t=7m30s) and as you can see in the video (at 7:30 and onward) the character with the green backpack is terribly lagging/teleporting but NOT HACKING! In this case it seems that the client is telling the server where the player has to be and not vice versa as it normally should be. So I'd say your "hacker" wasn't one... just the bad network technology :-/ Except the fact, that they could tell your nicknames.
Please excuse my bad english :)