How can I check if a player killed another player? [UNSOLVED]

I have a leaderboard script which has an IntValue called points. How could I add something into the leaderboard script that detects if a player has killed someone else, and so when a player kills someone they get +10 Value for the Points IntValue

ball = script.Parent
damage = math.random(10,30)
local hitt = false

HitSound = Instance.new("Sound")
HitSound.Name = "HitSound"
HitSound.SoundId = "http://www.roblox.com/asset/?id=11945266"
HitSound.Pitch = .8
HitSound.Volume = 1
HitSound.Parent = ball

function onTouched(hit)
	if hit.Parent:findFirstChild("ForceField") ~= nil then return end
	if hit.CanCollide == false and hit.Parent:findFirstChild("Humanoid") == nil then return end
	if hit.Parent.className == "Hat" and hitt == false then
		hitt = true
		hit:BreakJoints()
		hit.Velocity = ball.Velocity
		hit.Parent.Parent = game.Workspace
	end

	if hit:findFirstChild("Metal") ~= nil and hitt == false then
		hitt = true
		for i = 1,math.random(1,3) do
			local j = Instance.new("Part")
			j.formFactor = "Plate"
			j.Size = Vector3.new(1,.4,1)
			j.BrickColor = BrickColor.new("Bright yellow")
			j.CanCollide = false
			j.Velocity = Vector3.new(math.random(-10,10),math.random(-10,10),math.random(-10,10))
			j.CFrame = script.Parent.CFrame
			j.Parent = game.Workspace
		end
	end

	local humanoid = hit.Parent:findFirstChild("Humanoid")

	if humanoid ~= nil and hitt == false then
		hitt = true
		tagHumanoid(humanoid)
		if hit.Name == "Head" then
			humanoid.Health = humanoid.Health - damage * 2
		elseif hit.Name == "Torso" then
			humanoid.Health = humanoid.Health - damage * 1.5
		else
			humanoid.Health = humanoid.Health - damage
		end
		wait(.1)
		untagHumanoid(humanoid)
	end
	if hitt == true then
		HitSound:play()
		ball.Parent = nil
	end
end

function tagHumanoid(humanoid)
	-- todo: make tag expire
	local tag = ball:findFirstChild("creator")
	if tag ~= nil then
		local new_tag = tag:clone()
		new_tag.Parent = humanoid
	end
end


function untagHumanoid(humanoid)
	if humanoid ~= nil then
		local tag = humanoid:GetChildren()

		for i = 1, #tag do

			if tag[i].Name == "creator" then
			tag[i]:remove()
			end
		
		end
	end
end

connection = ball.Touched:connect(onTouched)

while true do
wait(.01)
if damage < 0 then
break
else
damage = damage - .2
end
end

ball.Parent = nil

You need to create a StringValue called "creator" in the person's humanoid with the value of the person who killed them. Have you leaderboard check when someone dies and see if that "creator" value has been created, if so, then use that value to add kills to the player who killed that player.