Gun fires, but doesn't kill humanoid?

UPDATE: Hit is defined, line 12

This script is inside a tool, meant to kill Zombies (Hostile NPCs with a Humanoid named Zombie), and when the tool is fired the ball(bullet) kills the Zombie. It works on test mode in ROBLOX Studio, but not when a physically play the game. Script looks very long, but all I worry about are lines 12-34

--Script looks very long, but all I worry about are lines 12-34
ball = script.Parent
damage = math.random(30,60)
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("Zombie") == 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("Zombie")

    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(.2)
        untagHumanoid(humanoid)
    end
    if hitt == true then
        HitSound:play()
        ball.Parent = nil
    end
end

function tagHumanoid(humanoid)
    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:findFirstChild("creator")
        if tag ~= nil then
            tag.Parent = nil
        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

The ball(bullet) spawns when fired, but does not take any damage to the Zombie. The scripting is correct, no errors, bullet spawns works on studio but not when played. Please help!