The talent's description reads:
"Killing an enemy with a headshot guarantees that the next shot will be a (critical) guaranteed headshot."
(in brackets: Perfectly Determined)
While the talent currently does work as described, it probably does not work as intended. Because as it is now you only need one initial headshot kill to then basically have an endless chain of one-shot-kills, all being considered headshots by the game, despite never hitting any head again. This leads to drastically overpowered builds especially with the (Perfect) Headhunter talent.
A solution could be to change the talent to align with the description of for example the Achilles Pulse:
"Killing an enemy with a headshot guarantees that the next shot will deal (critical) headshot damage."
The difference lies in either guaranteeing a headshot or guaranteeing headshot damage. This for the game's logic is a crucial difference.
Other solutions would be to add a cooldown to the talent...
"Killing an enemy with a headshot guarantees that the next shot will be a guaranteed headshot. After activation talent goes on cooldown for 20 seconds (10 seconds)."
(in brackets: Perfectly Determined)
...or having to again activate the talent with actual headshots:
"Killing an enemy with a headshot guarantees that the next shot will be a (critical) guaranteed headshot. Talent goes on cooldown after activation until hitting a target in the head."