Tenant getting harassed by a neighbor

[Matthew Lessard]

Hi All,

My tenant is getting passively harassed by a neighbor. I do not know who the neighbor is but they seem to be targeting him. He has been a great long term tenant and I am confident he isn't doing anything to provoke such action. 

The latest incident was the neighbor dug through his trash, found a few bags that weren't tied all the way and reported him to the city. The city eventually hand delivered a letter to him that he needs to tie his trash bags. If you are thinking that this is a joke I completely understand. Unfortunately it is not, this actually happened.

I feel terrible that he is going through this and also frustrated that I cant take any action as I don't know who the culprit is.  Also, I do not want to lose a good long term tenant or have the same thing happen to future tenants. Does anyone have advice on how to handle this? I thought about speaking with an attorney but I don't know what good it will do since I don't know who it is and have no proof. 

The house is located in a good area with an HOA in Tempe, AZ. Any input would be much appreciated.

Thanks,

-Matt