I agree with what @AF2603 said, you put MouseButton1Down but with tools, it should be tool.Activated
or local mouse = game.Players.LocalPlayer:GetMouse() mouse.MouseClick:Connect(function()
As everyone else said, you should use Tool.Activated, other than that it should work if you unhighlight it. It does not need to be inside of the Equipped function, leave it outside.
As for playing the animation, you should use the Animator object inside of the Humanoid, Humanoid:LoadAnimation() is deprecated, whilst Animator:LoadAnimation() is not. Everything using the animator is the same, it is just located inside of the Humanoid.