My Gun is damaging Pathfinding NPCs, but its not killing them?

So I'm using a raycasting gun and when I fire it at a NPC , the NPC reaches 0 health but doesnt die and keeps following me? Here is the scripts. Oh and by the way they are holding a sword because they are ninjas.

  local tool = script.Parent
    local player = game:GetService("Players").LocalPlayer

    tool.Equipped:connect(function(mouse)
        print("Tool equipped!")

        mouse.Button1Down:connect(function()
            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("White")
            beam.FormFactor = "Custom"
            beam.Material = "Plastic"
            beam.Transparency = 0.6
            beam.Anchored = true
            beam.Locked = true
            beam.CanCollide = false

            local distance = (tool.Handle.CFrame.p - position).magnitude
            beam.Size = Vector3.new(0.3, 0.3, distance + 5)
            beam.CFrame = CFrame.new(tool.Handle.CFrame.p, position) * CFrame.new(0, 0, -distance / 2)

            game:GetService("Debris"):AddItem(beam, 0.1)

            if part then
                local humanoid = part.Parent:FindFirstChild("Humanoid")

                if not humanoid then
                    humanoid = part.Parent.Parent:FindFirstChild("Humanoid")
                end

                if humanoid then
                    script.Parent.Fire:Play()
                                        humanoid:TakeDamage(40)

                end
            end
        end)
    end)

Thanks!