Mr. Carbuff and his friends have hiked the AT through Bear Mountain and Harriman parks. 2016, I think, so the year before MH would have been there.
There were flyers there last fall, I am told, though I did not witness it myself.
He may have been bandit camping. Because Bear Mountain is accessible from NYC, they tend to attract quite a few homeless/transient types. It's also pretty close to several towns, and across the river from Peekskill, a small city. There are summer camps and tourist facilities everywhere. In the summer, it's packed wall to wall with people. Not as busy in late spring, but lots of boy scout troops doing day or overnight hikes in the area.
There are RV camping facilities, several tent campgrounds nearby but not right at the headquarters, an inn, public restrooms and so forth--pretty much everything you'd need for extended visit. AT through hikers often stay at the inn overnight to rest, sleep in a bed, get a shower, etc. etc.
I think the map of the area has been posted before but here it is again:
Google Maps
