How could I make a 3rd person camera script similar to POLYGUNS?

NOTE: This will glitch out when you are in roblox studio, so when you press play, and it doesn't work, just stop it and play it again.

I've actually managed to do this w/ help of the people on the devforums. Create 2 local scripts in StarterPlayer> StarterPlayerScripts. Name them what you would like. ( I named the first one CamOffset, and the second one MouseLock.)

The CamOffset Script will make it so you get a shoulder view perspective. The mouse lock makes it so you don't need to right click to look around.

Code in CamOffset:

-------------
--- INDEX ---
-------------

--Services
local userInputService = game:GetService("UserInputService")
local runService = game:GetService("RunService")

--Player & Character
local localPlayer = game:GetService("Players").LocalPlayer

--Other
local Camera = game:GetService("Workspace").CurrentCamera

--------------
--- VALUES ---
--------------

local xAngle = 0
local yAngle = 0
local cameraPos = Vector3.new(3.5,0,7.5)

----------------------
--- INITIALIZATION ---
----------------------

wait(1)
Camera.CameraType = Enum.CameraType.Scriptable
userInputService.MouseBehavior = Enum.MouseBehavior.LockCenter

-----------------
--- FUNCTIONS ---
-----------------

userInputService.InputChanged:Connect(function(input)
    if input.UserInputType == Enum.UserInputType.MouseMovement then
        xAngle = xAngle-input.Delta.x*0.4
        --Clamp the vertical axis so it doesn't go upside down or glitch.
        yAngle = math.clamp(yAngle-input.Delta.y*0.4,-80,80)
    end
end)

runService.RenderStepped:Connect(function()
    local Character = localPlayer.Character
    local rootPart = Character:FindFirstChild("HumanoidRootPart")
    if Character and rootPart then
        --Set rotated start cframe inside head
        local startCFrame = CFrame.new((rootPart.CFrame.p + Vector3.new(0,2,0)))*CFrame.Angles(0, math.rad(xAngle), 0)*CFrame.Angles(math.rad(yAngle), 0, 0)

        --Set camera focus and cframe
        local cameraCFrame = startCFrame + startCFrame:vectorToWorldSpace(Vector3.new(cameraPos.X,cameraPos.Y,cameraPos.Z))
        local cameraFocus = startCFrame + startCFrame:vectorToWorldSpace(Vector3.new(cameraPos.X,cameraPos.Y,-50000))

        Camera.CFrame = CFrame.new(cameraCFrame.p,cameraFocus.p)
    end
end)

Code In MouseLock:

local SENSITIVITY = 100
local DISTANCE_Y = 3
local DISTANCE_Z = 12

local BEHAVIOR_LOCK_CENTER = Enum.MouseBehavior.LockCenter
local BEHAVIOR_DEFAULT = Enum.MouseBehavior.Default
local TYPE_MOUSE_MOVEMENT = Enum.UserInputType.MouseMovement

local UserInputService = game:GetService("UserInputService")
local Camera = workspace.CurrentCamera
local HumanoidRootPart = game:GetService("Players").LocalPlayer.Character.HumanoidRootPart

-- Property for changing whether player can move mouse freely or not
local IsLocked = false

-- X and Y values for camera
local X, Y = 0, 0

UserInputService.InputChanged:Connect(function(InputObject)
    if InputObject.UserInputType == TYPE_MOUSE_MOVEMENT then
        local Delta = InputObject.Delta
        X = X + (Delta.Y / SENSITIVITY)
        Y = math.clamp(Y + (Delta.Y / SENSITIVITY), -1, 1.5)
    end
end)

game:GetService("RunService").RenderStepped:Connect(function()
    if IsLocked then
        UserInputService.MouseBehavior = BEHAVIOR_LOCK_CENTER
    else
        UserInputService.MouseBehavior = BEHAVIOR_DEFAULT
    end

    Camera.CoordinateFrame =
        CFrame.new(HumanoidRootPart.Position)
        * CFrame.Angles(0, X, 0)
        * CFrame.Angles(Y, 0, 0)
        * CFrame.new(0, DISTANCE_Y, DISTANCE_Z)
end)

And that should be it.