Why wont my custom mouse image load?

Whenever I make it so that the mouse icon changes correspondingly to when the gun is equipped or when it's reloading, it shows an error saying that it failed to load. Why is it doing that? Has anyone else experienced this?

--MADE BY MR_UNLUCKY
local tool = script.Parent
local player = game:GetService("Players").LocalPlayer
local Reload = tool.Reload
local Shoot = tool.Shot 
local GUI = tool.ScreenGui
local damageBODY = 10
local damageHEAD = 30
local Equip = tool.Equip
local bullets = 15
local Players = game:GetService("Players")
local mouse = game.Players.LocalPlayer:GetMouse()
tool.Equipped:connect(function(mouse)
    print("Tool equipped!")
    local newGUI = GUI:Clone()
    newGUI.Parent = Players.LocalPlayer.PlayerGui
    Players.LocalPlayer.PlayerGui.ScreenGui.Frame.Bullets.Text = "Bullets:"..bullets..""
    Players.LocalPlayer.PlayerGui.ScreenGui.Frame.GunName.Text = tool.Name
    mouse.Icon = "http://www.roblox.com/asset?id=936803887"
    mouse.Button1Down:connect(function()
        if bullets <= 0 then
            Reload:Play()
            mouse.Icon = "http://www.roblox.com/asset?id=43557168"
            Players.LocalPlayer.PlayerGui.ScreenGui.Frame.Bullets.Text = "RELOADING"
            wait(3.2)
            bullets = 15    
            Players.LocalPlayer.PlayerGui.ScreenGui.Frame.Bullets.Text = "Bullets:"..bullets..""
            mouse.Icon = "http://www.roblox.com/asset?id=936803887"
        else
        print("Mouse pressed!")
        local ray = Ray.new(tool.Handle.CFrame.p, (mouse.Hit.p - tool.Handle.CFrame.p).unit * 300)
        local part, position = workspace:FindPartOnRay(ray, player.Character, false, true)
            local beam = Instance.new("Part", workspace)
            beam.BrickColor = BrickColor.new("Medium stone grey")
            beam.FormFactor = "Custom"
            beam.Material = "Metal"
            beam.Transparency = 0.25
            beam.Anchored = true
            beam.Locked = true
            beam.CanCollide = false
            bullets = bullets - 1
            print(bullets)
            local distance = (tool.Handle.CFrame.p - position).magnitude
            beam.Size = Vector3.new(0.3, 0.3, distance)
            beam.CFrame = CFrame.new(tool.Handle.CFrame.p, position) * CFrame.new(0, 0, -distance / 2)
            Shoot:Play()        
            game:GetService("Debris"):AddItem(beam, 0.1)
            Players.LocalPlayer.PlayerGui.ScreenGui.Frame.Bullets.Text = "Bullets:"..bullets..""
            if part then
            local rightLeg = part.Parent:FindFirstChild("RightLeg")
            local leftLeg = part.Parent:FindFirstChild("LeftLeg")
            local rightArm = part.Parent:FindFirstChild("RightArm")
            local leftArm = part.Parent:FindFirstChild("LeftArm")
            local torso = part.Parent:FindFirstChild("Torso")
            local head = part.Parent:FindFirstChild("Head")
            local humanoid = part.Parent:FindFirstChild("Humanoid")
            if not rightLeg or leftLeg or rightArm or leftArm or torso or head then
                local rightLeg = part.Parent:FindFirstChild("RightLeg")
                local leftLeg = part.Parent:FindFirstChild("LeftLeg")
                local rightArm = part.Parent:FindFirstChild("RightArm")
                local leftArm = part.Parent:FindFirstChild("LeftArm")
                local torso = part.Parent:FindFirstChild("Torso")
                local head = part.Parent:FindFirstChild("Head")
            end
            if rightLeg or leftLeg or rightArm or leftArm or torso then
                humanoid:TakeDamage(damageBODY)
            end
            if head then
                humanoid:TakeDamage(damageHEAD)
            end
end
end
tool.Unequipped:connect(function(mouse)
    Players.LocalPlayer.PlayerGui:FindFirstChild("ScreenGui"):Destroy()
end)
    end)
    end)