Any idea as to why my script creates a lag spike in the game?

So what I have here is an opensource script that is very unique. Nothing quite like it. What it is is just a death but your character explodes in tiny little particle squares. This is very fitting in my game.

Here's the script

local FORCE = 25 -- max sideways velocity
local UP_VELOCITY = 70 -- max upwards velocity
local AMT = 10 -- per stud^3
local AFFECTED_BY_PHYSICS = true -- whether or not to let the particles interact with the world - if false, they will be removed on contact
local DURATION = 15 -- how long the particles stay visible for

local particleGUIs = {}
local particleModel = Instance.new("Model", workspace)
particleModel.Name = "ParticleContainer"

game.Players.PlayerAdded:connect(function(player)
    player.CharacterAdded:connect(function(character)
        local humanoid = character:WaitForChild("Humanoid")
        humanoid.Died:connect(function()
            print("Done")
            character.HumanoidRootPart:Destroy()
            for _, limb in pairs(character:GetChildren()) do
                if limb:IsA("BasePart") then
                    for i = 1, limb:GetMass() * AMT do
                        local p = Instance.new("Part", particleModel)
                        p.Name = "Particle"
                        p.CanCollide = false
                        p.FormFactor = Enum.FormFactor.Custom
                        p.Size = Vector3.new()
                        p.CFrame = limb.CFrame
                        p.Velocity = Vector3.new(math.random()*2-1, 0, math.random()*2-1).unit * FORCE + Vector3.new(0, math.random()*UP_VELOCITY, 0)
                        p.CanCollide = AFFECTED_BY_PHYSICS
                        if not AFFECTED_BY_PHYSICS then p.Touched:connect(function(hit) if hit.Name ~= "Particle" then p:Destroy() end end) end
                        p.Transparency = 1
                        local gui = Instance.new("BillboardGui", p)
                        gui.Adornee = p
                        gui.Size = UDim2.new(0.5, 0, 0.5, 0)
                        local square = Instance.new("ImageLabel", gui)
                        square.BorderSizePixel = 0
                        square.Size = UDim2.new(1, 0, 1, 0)
                        square.BackgroundColor3 = limb.BrickColor.Color
                        table.insert(particleGUIs, square)
                    end
                    limb:Destroy()
                end
            end
        end)
    end)
end)

while true do
    local elapsed = wait(15)
    for index, particle in pairs(particleGUIs) do
        particle.BackgroundTransparency = particle.BackgroundTransparency + elapsed/DURATION
        if particle.BackgroundTransparency > 1 then
            particleGUIs[index] = nil
            particle.Parent.Parent:Destroy()
        end
    end
end

Thank you! You guys are the best.``