How do I check who killed someone else?

I am trying to figure out how to award points for killing, but I do not know how to check for the killer, I only know how to check for the one that has been killed, this is what I have tried so far:

function awardpoints(player,points)
    if player and points then
        local leaderstats = player:FindFirstChild("leaderstats")
        if leaderstats then
            local pointsvalue = leaderstats:FindFirstChild("Points")
            if pointsvalue then
                pointsvalue.Value = pointsvalue.Value + points

            end
        end
    end
end
function awardexp(player,exp)
    if player and exp then
        local leaderstats = player:FindFirstChild("leaderstats")
        if leaderstats then
            local expvalue = leaderstats:FindFirstChild("exp")
            if expvalue then
                expvalue.Value = expvalue.Value + exp

            end
        end
    end
end
game.Players.PlayerAdded:connect(function(player)
    player.CharacterAdded:connect(function(character)
        character:WaitForChild("Humanoid").Died:connect(function()
            local tag = character.Humanoid:FindFirstChild("creator")
            if tag ~= nil then
                if tag.Value then
                    local KillerTag = character:FindFirstChild("KillerTag")
                    if KillerTag then
                        awardpoints(player,50)
                        awardexp(player,100)
                    else
                        awardpoints(player,-500)
                        awardexp(player,-1000)
                    end
                end
            end
        end)
    end)
end)

This code rewards the player that got killed instead of the player that killed, there seems to be nothing wrong with the first two functions. Also it gives the right amount to the correlating person, but affects the one that got killed.