Tool animation isnt loading?

I first tried just making the animation in a local script but I was told I probably couldn't do that. I tried making it in a server script then playing it from a tool, but the animation still wont load.

-- Server Script
game.Players.PlayerAdded:Connect(function(plr)
	plr.CharacterAdded:Connect(function(char)
		if plr.Backpack:FindFirstChild("Knife") then
			local swingAnim = Instance.new("Animation",plr.Backpack.Knife)
			swingAnim.AnimationId = "rbxassetid://4928252907"
			swingAnim.Name = "knifeSwing"
		elseif char:FindFirstChild("Knife") then
			local swingAnim = Instance.new("Animation",char.Knife)
			swingAnim.AnimationId = "rbxassetid://4928252907"
			swingAnim.Name = "knifeSwing"
		end
	end)
end)

-- Tool Script
script.Parent.Activated:Connect(function()
	
	local swingAnim = script.Parent:WaitForChild("knifeSwing")
	local swingTrack = game.Players.LocalPlayer.Character.Humanoid:LoadAnimation(swingAnim)
	swingTrack:Play()
	print("swing")
end)