His injuries are reported to be "extensive, including several broken bones, but he said the teen was conscious and stable throughout the rescue" and is reported to have left the hospital:
http://www.seacoastonline.com/apps/pbcs.dll/article?AID=/20100824/NEWS/8240336
Some of the reports make it sound like the cause of the fall was a misstep on the trail (above ref). Others explicitly say he was "was rock climbing up Central Gully":
http://www.unionleader.com/article....rticleId=08bc67d4-612d-41e0-a52d-76eedf1e38c6
Another report says 'fell while climbing in the upper reaches of the Central Gully in the ravine, described as "the most difficult trail" in the White Mountains because of its "narrow," "steep" and "exposed" ledges'.
http://www.seacoastonline.com/articles/20100820-NEWS-8200376
(For those who may not know, Central Gully is the gully to the left of Huntington Ravine Tr as it ascends the headwall. I personally would not describe the trail as being in the gully--it is off to the right side.)
From the above reports, it appears likely that he may have been attempting to climb the gully (ie off the trail), but given that non-technical-climbers (and reporters...) often use the word "climb" to mean "hike upward", it is hard to tell. (Loose definition: for technical climbers, climbing requires the use of hands and likely ropes while hiking is walking on one's feet with little/no need for the use of hands.)
The name "Central Gully" also appears quite often in the reports. Given that Central Gully does not appear in the WMG (28th ed, pp 26-28) trail description, I suspect that many hikers are unaware of the name. However, IIRC there are places on the trail where if one falls one could end up in Central Gully, so it is possible the name was supplied by the rescuers, if indeed he did end up in the gully.
A final factor is that the threat of a rescue fine/charge gives those involved incentive to report that they were hiking (ie on the trail) rather than climbing (ie off the trail) if they actually were climbing off trail.
(The above articles were found by following roadtripper's link.)
Doug