I tow a banner around Manhattan 4 days a week at 1000ft. I didn't go today b/c ceilings @ linden were ~11-1200ft. Metar was reporting 1500 at Newark. Vis was around 5 mi over linden when I took off at 1300.
There are a few fixed wing sight seeing tours on the Hudson every day, but I have *never* seen one on the east river. Helo's everywhere, but apparently this isn't one of them. The only fixed wings on the east river are me, and a handful of amphibs who come in and out 2x a day.
My guess is that a tour, or a weekend warrior, decided to take it up the east river. They either botched the 180 over rosevelte island (maybe a left hand turn northbound to southbound with the 15kt east wind today), or they had engine trouble and tried to take it west to central park, hitting the building enroute. You have a 'box canyon' of sorts with laguardia's airspace up there. I make 180's there all the time though towing a 50'x100' banner, so I don't see how this would really be the reason.
I have a feeling this is going to screw up my current job. My livelyhood depends on the exclusion.