When a player dies we enter EEKilled() in scripts. As arguments we get the target (PlayerBase) and the source of death (Object) . Sometimes when a player kills another player the source will be the same as the target instead of the actual killer. This is incorrect and started to go wrong in patch 1.20. Before that it worked fine. the source should have been the killers PlayerBase. The only time the source should be the same as the killer is when the player run out of health due to starvation/bleed out etc or if he suicided (f11).

You can see this in the adminlogs where you will get the specific logs for when a player died of natural causes or suicide. Its in that scope "(player == source)"

the admin logs looks like following:

21:56:55 | Player "Hidden" (DEAD) (id=FGVmVTQ8NwPVhxMcOqWjsxSElEfJXxMi3ST4LQ-gSR4= pos=<8374.3, 4947.5, 140.5>)[HP: 0] hit by Player "metropoliten666" (id=kdKBUutz7Syg30RZYy9UFKPs1ZFJqixI2DVgiTmyqIA= pos=<8378.2, 4942.1, 140.1>) into Head(0) for 110 damage (Bullet_12GaugeSlug) with IZH-43 from 6.70112 meters
21:56:55 | Player "Hidden" (DEAD) (id=FGVmVTQ8NwPVhxMcOqWjsxSElEfJXxMi3ST4LQ-gSR4= pos=<8374.3, 4947.5, 140.5>) died. Stats> Water: 708.594 Energy: 1575.17 Bleed sources: 0

this is how logs should look when its pvp:
21:49:18 | Player "Sven" (DEAD) (id=h9m8432czgibcFiHdra8cnx0ASEQvPPV4yA7MVi6Rgc= pos=<3957.8, 8600.2, 308.4>) killed by Player "2pac" (id=_NGgE3a4lfU2GJGr8br4XHHyQWELp5vqfgIj7Tx9L0g= pos=<3960.5, 8598.8, 308.2>) with SSG 82 from 3.06566 meters

For vanilla this is mainly a problem for admins who is helping players solving ingame dayz issues.
For modding its a lot worse since we cant know what killed the player for sure and in many cases we cant find out who.