how do i make my knife only kill npcs aka zombies?

ive been trying to figure out how to make my knife only kill npcs and not people but can't seem to figure out how to do it after attempting many solutions.

local Handle = script.Parent; 
local Tool = Handle.Parent; 
local Config = Handle:WaitForChild("Configuration"); 
local Sounds = Config:WaitForChild("Sounds"); 
local StabE = Config:WaitForChild("StabE"); 
local ThrowE = Config:WaitForChild("ThrowE"); 
local Throw = false; 

function Throw(Target) 
    local Flying = false;
    local NewBlade = Handle:Clone(); 
    NewBlade.Parent = workspace; 
    NewBlade.Anchored = false;
    NewBlade.CanCollide = false; 
    NewBlade.Locked = true; 
    NewBlade.Transparency = 0; 
    local CloneFly = Sounds.Fly:Clone()
    local CloneHit = Sounds.Hit:Clone()
    local CloneTing = Sounds.Ting:Clone()

    CloneHit.Parent = NewBlade
    CloneFly.Parent = NewBlade
    CloneFly:Play()

    NewBlade.Velocity = (Target - NewBlade.CFrame.p).unit * 100; 
    NewBlade.CFrame = CFrame.new(NewBlade.CFrame.p, NewBlade.CFrame.p + NewBlade.Velocity) * CFrame.Angles(0, 0, math.rad(-90)); 

    local FlyForce = Instance.new('BodyForce', NewBlade);
    FlyForce.force = Vector3.new(0, 196.2 * NewBlade:GetMass() * 0.98, 0);
    local Spiral = Instance.new('BodyAngularVelocity', NewBlade); of the blade as it flies
    Spiral.angularvelocity = NewBlade.CFrame:vectorToWorldSpace(Vector3.new(0, -400, 0));

    NewBlade.Touched:Connect(function(hit) 
        if hit.Parent:FindFirstChild("Humanoid") and Tool.Parent ~= hit.Parent then 
            CloneHit:Play();
            local Hum = hit.Parent.Humanoid;
            Hum.Health = 0; 
            NewBlade:Destroy(); 
            print("Blade cleaned!");
        elseif not hit.Parent:FindFirstChild("Humanoid") and not hit.Parent.Parent:FindFirstChild("Humanoid") then
            CloneTing:Play();
            NewBlade:Destroy(); 
            print("Blade cleaned!");
        end
    end)
end

function Stab()
    local Blade = Handle;

    Blade.Touched:Connect(function(hit)
        wait();
        if hit.Parent:FindFirstChild("Humanoid") and Tool.Parent ~= hit.Parent then 
            wait();
            Sounds.Hit:Play();
            local Hum = hit.Parent.Humanoid; 
            Hum.Health = 0; 
            print("Player killed!");
        elseif not hit.Parent:FindFirstChild("Humanoid") and not hit.Parent.Parent:FindFirstChild("Humanoid") then
            wait();
            Sounds.Ting:Play();
            print("Hit the wall!")
        end
    end)
end


ThrowE.OnServerEvent:Connect(function(Throwing, Start)
    local Target = Start[2]
    Throw(Target)
end)
StabE.OnServerEvent:Connect(function()
    Stab()
end)