Image 1... titled "Orientation Lines" [link to imageshack.us
A 3 picture graphic of screen captures of the Youtube helicopter footage, and 2 from Bing maps of the Sandy Hook school, one a vertical view, the other an oblique view. The red lines connect the same feature as seen in each of the captures.
Image 2... titled "Sun Angle" [link to imageshack.us
This image uses the same Youtube and Bing maps vertical view captures as seen in the previous image. In the left image, the red lines indicate the start and end points of a standing person. These locations can be eyed relatively accurately and transferred to the right vertical view as indicated by the green lines and red dots. The black line is parallel to an imaginary line drawn through the red dots of the start and end shadow points (so as not to obscure the red dots).
The blue line is drawn north-south as is the north arrow on the right. The angle between the blue and black lines represents the sun's azimuth (by definition the sun's angle from north measured clockwise), resulting in an azimuth of approximately 178 degrees. This is obviously very close to due south, which equally obvious, indicates a time of around noon for the helicopter footage.
More precision can be found by utilizing an azimuth vs. time calculator for specific geographic locations and date. See image 3, Newtown, Dec. 14. [link to imageshack.us
From this chart, 178 degrees of azimuth puts the time for the helicopter footage around 11:40.
The largest source of error in this analysis is eyeballing the shadow placements on the Bing maps vertical image. Even being off by as much by as 5 degrees (though I'm confident the placements are not this inaccurate) the time of the helicopter footage would still be pinned between 11:20 and 12:00.