Behead II loses the stolen modifiers if the same skill kills another mob

If you steal modifiers from a rare mob with a skill with Behead II supporting it, and then use that same skill to kill something else like a white (normal) mob, you lose the modifiers from behead 2 instantly.

Tested with Killing Palm to steal mods from a Antlion Charger rare, and then losing them with 15s remaining on using Killing Palm to cull a normal white quadrilla in act 3.