How can I prevent team killing?

I created a gun script but it allows team killing how can I edit it to remove this possibility?

Here is my code:

--player variables
local player = game.Players.LocalPlayer
local mouse = player:GetMouse()

--gun variables
local gun = script.Parent 
local ammo = 100
local magammo = ammo
local reloading = false
local auto = false -- set to false if you do not want the gun to be automatic
local firing = false
local CanChangeFireModes = false
local damage = 80, 100
--^^If set to true the player can press v to change firemodes from auto to semi and semi to auto

local debounce = false

if not game.workspace:FindFirstChild("Bullet") then
	local bullet_storage = Instance.new("Folder", workspace)
	bullet_storage.Name = "Bullet"
else
	--nothing
end

function getBullet()
	print(ammo)
	if ammo > 0 then
		if debounce == false then
			debounce = true
			ammo = ammo - 1
			gun.Handle.Fire:Play()
			local mh = mouse.Hit
			local B = Instance.new("Part", workspace.Bullet)
			B.CFrame = gun.Handle.CFrame + (player.Character.Torso.CFrame.lookVector)
			B.CFrame = CFrame.new(B.Position, mh.p)
			B.FormFactor = "Custom"
			B.Size = Vector3.new(0.2, 0.2, 0.2)
			B.BrickColor = BrickColor.Black()
			B.CanCollide = false
			local velo = Instance.new("BodyVelocity", B)
			velo.velocity = B.CFrame.lookVector * 120
			velo.maxForce = Vector3.new(math.huge, math.huge, math.huge)
			B.Touched:connect(function(hit)
				local humanoid = hit.Parent:FindFirstChild("Humanoid")
				if humanoid then
					humanoid:TakeDamage(damage)
				end
			end)
		wait(0)
		debounce = false
		end
	end
end

function autofire()
	if ammo > 0 then
		while firing == true do
			if firing == true and ammo <= 0 then
				firing = false
			end
			print(ammo)
			wait(0)
			gun.Handle.Fire:Play()
			local mh = mouse.Hit
			local B = Instance.new("Part", workspace.Bullet)
			B.CFrame = gun.Handle.CFrame + (player.Character.Torso.CFrame.lookVector)
			B.CFrame = CFrame.new(B.Position, mh.p)
			B.FormFactor = "Custom"
			B.Size = Vector3.new(0.2, 0.2, 0.2)
			B.BrickColor = BrickColor.Black()
			B.CanCollide = false
			ammo = ammo - 1
			local velo = Instance.new("BodyVelocity", B)
			velo.velocity = B.CFrame.lookVector * 120
			velo.maxForce = Vector3.new(math.huge, math.huge, math.huge)
			B.Touched:connect(function(hit)
				local humanoid = hit.Parent:FindFirstChild("Humanoid")
				if humanoid then
					humanoid:TakeDamage(damage)
				end
			end)
		wait(0.005)
		end
	end
end

mouse.Button1Down:connect(function()
	if auto == true then
		firing = true
		autofire()
	else
		getBullet()
	end
	if ammo <= 0 then
		print('reloading')
		wait(2)
		ammo = magammo
	end
end)

mouse.Button1Up:connect(function()
	if firing == true then
		firing = false
	end
end)

local uis = game:GetService("UserInputService") -- allows firemode change
uis.InputBegan:connect(function(inputObject, gameProcessedEvent)
	if inputObject.KeyCode == Enum.KeyCode.V and CanChangeFireModes == true then
		if auto == true then
			auto = false
		else
			auto = true
		end
	end
end)

You could use values as in when a player is assigned a team then a Value is parented under his character and add a value to the gun he uses that identifies what team he is on and it changes every time he changes team and then you could make a touched event with the bullet and make it to where if the bullet touches a part and the guns value which identifies the team that the gun is under and if the character that gets touched by that has the same value inside of him you could make it return end and then if the character that gets touched by it doesn't have that value he would take damage so you won't have to worry about the team players getting hurt because they will have the same value as the gun that the bullet is getting shot out of... It might be a bit complicating but, I hope you understood what I meant and I am sorry if you didn't. You can comment below for any questions or concerns!