Used to have a 5 story tall tree in our backyard, one day a big branch fell into the neighbor's yard. They complain for safety reason and we agree. We ask them to write us a letter and use that as evidence just in case some tree huggers want us to preserve it.
We hired a company to remove it. A "Rambo" climb all the way to the top and each branch's tip, chain saw a chunk at a time, and spend a whole day removing it. That cost $3k in 1995 dollar.
Glad that tree is gone or someone would be killed sooner or later within a few decades, just a matter of time.