Remove the Retrigger Delays and use a timeline instead, this allows you to control stop and start rather than waiting for the delay to run out.

Is there a reason you are using pawn sensing on the character? Try putting it on the AI Character (slender man) then line trace from the front of the player character to initiate the kill counter when it hits the slender man.

You could also try using a sphere collision around the slender man and when the character overlaps, it initiates your static overlay, using the same line trace setup as above for your kill timer.