How to transfer liability for tree back to neighbor?

[Jack B.]

My neighbor at a house I recently sold wanted me to cut down a tree that he felt was a danger to his property, conveniently after I called the cops on him for repeatedly parking in my driveway and refusing to move his vehicles... 

The previous owner mentioned to me that she had wanted to take the tree down but this same neighbor didn't want it taken down since his kids played around it. 

I told the neighbor that the tree looks the same as it did when the house was built a few years ago, what makes him think that it's a danger? He responded by getting a guy from 120 miles away who had been an arhborist for 6 months at the time (mind you we live in a major city, there are dozens of arbhorists within a few miles of us...he was shopping for someone who was purely new and would say anything for business IMO) to illegally trespass on my property to assess the tree. He then sent me a certified letter with the results and requesting the tree to be taken down (which I had previously told him he could do at his own expense via text when he had originally contacted me). I sold the house a year later, how do I transfer liability for the tree back to the neighbor? Send a certified letter letting him know there is a new owner?