I did not observe this issue myself but have gathered some info and am sharing it in case it is any help in resolving the problem.

It has been reported that cheaters are able to remotely kill players by teleporting bullets to them.

The original post describing the issue is here: http://www.reddit.com/r/dayz/comments/2uws15/scripters_can_still_instantly_kill_you_in_53_dayz/

A poster replied in that thread as follows: "The battleye update did not stop murder mode using WPM, however. You can still write a bullet's Vector3 to your clientside memory and that bullet will teleport into someone's head if you tell it to."

I googled 'murder mode' and found the following link that seems to correspond to what was said by the second poster: http://www.unknowncheats.me/forum/dayz-sa/129497-murder-mode-dayz-sa.html

The relevant info at that link is as follows:

"Murder mode basically kills everything in your radius with one shot(each?).

How do you do it?
It's simple. You just teleport your bullet into everyone's head around you.

Great! But how do I do that?
Another simple answer!
In DayZ SA 0.51, there is a "Bullet-Table" which basically stores bullets that are fired.
Where is this magical table you ask?
It's at
Code:

World] + 0x9AC]

It's size is at
Code:

World] +0x9B0]

Great! Now what?
Well each 0x4, there is a pointer to a bullet entity.
In this bullet entity, if you go to
Code:

bullet] + 0x44] + 0x28]

that's your D3DXVECTOR3 for position of the bullet.

If you go through the entity list, and find the head positions of all your targets, just teleport the bullet there, and BAM, they're dead.

Now you may ask where the head positions for entities are, they're here:
Code:

Entity] + 0x1C] +0x130]

Or 0x130 into the visual state."