When playing at night against enemy that are using flashlights, their flashlights will turn off as soon as they are killed.
This results in the player knowing that they have killed the target because their torch has gone out.
It's the same with a target's Laser Pointer, it'll turn off when they die.
Have not tested on multi-player PvP, but I presume it's the same.
My suggestion would be that the light stays on for a minute or two after the target dies.