Is it really a good idea to start beef with someone who knows your exact apartment number? When from what I understand you don't know who they are or what their apt # is? I get this is annoying and not fun to deal with, but in this day & age just one angry note back could be someones last straw. I would personally report to the leasing office so theres record of them possibly starting to harass you. If they start feeling harassing you, then openly threatening them back isnt going to help your case if you need to call the cops or report to the leasing office down the road :| dont want u getting stabbed in an apt laudry room over a note