How do you make a kills leaderboard include NPC kills?

I have the classic LinkedLeaderboard script, and it doesn't count the number of times I've killed NPCs. I'm not sure why, because the humanoids of the NPCs are named 'Humanoid' just like the player's is.

stands = {}
CTF_mode = false


function onHumanoidDied(humanoid, player)
	local stats = player:findFirstChild("leaderstats")
	if stats ~= nil then
		local deaths = stats:findFirstChild("Wipeouts")
		deaths.Value = deaths.Value + 1

		-- do short dance to try and find the killer

		local killer = getKillerOfHumanoidIfStillInGame(humanoid)

		handleKillCount(humanoid, player)
	end
end

function onPlayerRespawn(property, player)
	-- need to connect to new humanoid
	
	if property == "Character" and player.Character ~= nil then
		local humanoid = player.Character.Humanoid
			local p = player
			local h = humanoid
			humanoid.Died:connect(function() onHumanoidDied(h, p) end )
	end
end

function getKillerOfHumanoidIfStillInGame(humanoid)

	-- check for kill tag on humanoid - may be more than one - todo: deal with this
	local tag = humanoid:findFirstChild("creator")

	-- find player with name on tag
	if tag ~= nil then
		
		local killer = tag.Value
		if killer.Parent ~= nil then -- killer still in game
			return killer
		end
	end

	return nil
end

function handleKillCount(humanoid, player)
	local killer = getKillerOfHumanoidIfStillInGame(humanoid)
	if killer ~= nil then
		local stats = killer:findFirstChild("leaderstats")
		if stats ~= nil then
			local kills = stats:findFirstChild("KOs")
			if killer ~= player then
				kills.Value = kills.Value + 1
				
			else
				kills.Value = kills.Value - 1
				
			end
		end
	end
end

function findAllFlagStands(root)
	local c = root:children()
	for i=1,#c do
		if (c[i].className == "Model" or c[i].className == "Part") then
			findAllFlagStands(c[i])
		end
		if (c[i].className == "FlagStand") then
			table.insert(stands, c[i])
		end
	end
end

function hookUpListeners()
	for i=1,#stands do
		stands[i].FlagCaptured:connect(onCaptureScored)
	end
end

function onPlayerEntered(newPlayer)

	if CTF_mode == true then

		local stats = Instance.new("IntValue")
		stats.Name = "leaderstats"

		local captures = Instance.new("IntValue")
		captures.Name = "Captures"
		captures.Value = 0


		captures.Parent = stats

		while true do
			if newPlayer.Character ~= nil then break end
			wait(5)
		end

		stats.Parent = newPlayer

	else

		local stats = Instance.new("IntValue")
		stats.Name = "leaderstats"

		local kills = Instance.new("IntValue")
		kills.Name = "KOs"
		kills.Value = 0

		local deaths = Instance.new("IntValue")
		deaths.Name = "Wipeouts"
		deaths.Value = 0

		kills.Parent = stats
		deaths.Parent = stats

		while true do
			if newPlayer.Character ~= nil then break end
			wait(5)
		end

		local humanoid = newPlayer.Character.Humanoid

		humanoid.Died:connect(function() onHumanoidDied(humanoid, newPlayer) end )

		newPlayer.Changed:connect(function(property) onPlayerRespawn(property, newPlayer) end )


		stats.Parent = newPlayer

	end

end


function onCaptureScored(player)

		local ls = player:findFirstChild("leaderstats")
		if ls == nil then return end
		local caps = ls:findFirstChild("Captures")
		if caps == nil then return end
		caps.Value = caps.Value + 1

end


findAllFlagStands(game.Workspace)
hookUpListeners()
if (#stands > 0) then CTF_mode = true end
game.Players.ChildAdded:connect(onPlayerEntered)