Why does it say I don't kill anyone post game ?

When I play with friends and I don't get a kill according to the post match screen, I just chalk it up to whatever. But I was playing a solo game in Duo's and downed someone and killed their teammate, which eliminated the squad, but the post game still read that I did not get a kill. Do I have to outright kill the player first before eliminating the others on the team for it to count, or do I just not understand how the kill system works in the game ?