Hi bro, here goes a ideia..
1) Declare a ID variable to identify each player.
2) Make a Function to calculate the damage on the enemy and send the ID variable to the function
3) In the function, use this logic IF THE ENEMY HP WAS > 0 AND ITS <=0 NOW this player ( ID ) got the kill
dont use ALL the premade functions at the C2, the program is made to help you in 95% off the cases but you still need to work on that 5%.
Sorry my bad english, im Brazilian.