I'd also be interested to know the type and circumstances if anybody knows.
It is worthy of mention that around the world most countries have a "lightweight" deregulated category below which airworthiness and licencing rules are relaxed.
Here in the UK, this line is at 450kg/990lb, with a 35 knot stalling speed. However, the aircraft are still "certified" and the pilots still have to complete a PPL course, pass a skills test, and maintain a minimum level of currency. Pilots trained on other types have to do some kind of conversion.
In the USA, the line is single seat / 115kg/254lb empty, with a maximum speed of 55 knots. To fly these light single seaters you need no licence, no registration (although that may be changing), and no form of airworthiness approval for the aeroplane.
Whilst I'd not wish to prejudge either the pilot or aircraft in this case, it's likely that US ultralights have a poorer safety record than UK microlights (or most other countries with their own flavours of "light touch" light aviation).
The other thing often missed is that aeroplanes that small and light / low energy do not handle or perform like a bigger faster aeroplane (say a C150!). Pilots experienced and safe on such aeroplanes are not necessarily safe on a single seat aeroplane with a take-off weight around 500 lbf. (Or vice versa of course).
(Conversely, in the USA gliders have to have an ICAO compliant CofA and pilots a PPL, whilst in the UK it was until very recently quite legal to build and fly a glider on your own with no controls whatsoever. Of-course, the BGA made sure this didn't really happen, just as the USUA does it's best to keep ultralight flying safe in America).
G