Why does the bullet from my turret not kill?

I have a turret that fires a part. I want this part to kill the person it touches, but it does not kill. The turret DOES fire the part, but it does not KILL. Please help

gun = script.Parent
gunPos= gun.Position

function firePart()
	local part = Instance.new("Part",workspace)
	part.Size = Vector3.new(1,1,1)
	part.Material = "SmoothPlastic"
	part.Position = gunPos
	part.Velocity = Vector3.new(0,0,-150)
end
wait(3.2)
while true do
	firePart()
	wait(0.2)
	firePart()
	wait(0.2)
end

local part = Instance.new("Part",workspace)

script.Parent.Touched:connect(function(hit)
	if hit and hit.Parent and hit.Parent:FindFirstChild("Humanoid") then
		hit.Parent.Humanoid.Health = 0
	end
end)