I will complete my more detailed analysis of these events at a later time and likely via video.
Many hoaxers, such as Jim Fetzer, claim that the photos are from a drill in October. While that is idiotic disinformation on it's face, I wanted to point out that the evacuation of children is occurring with at least one photographed officer taking a position of cover, protecting the children.
Shannon Hicks' photo is below. This is a high resolution version; click to enlarge.
If you look closely, you can see Newtown Officer William Hull in the background. Officer Hull was on an extra duty assignment prior to responding.
Officer Hull had arrived very early and took a position covering parents who were hiding behind the dumpsters on the (essentially) south side of the school. His arrival at 9:46 is documented on Seabrook's Dash Cam and by radio. Obviously, this is not an "October School Drill"; the children are escorted under armed cover.
Later, at 10:43, we see Officer Hull return and get crime scene tape. The events match his statement. As can been seen, soon after Hull's arrival, he removed his bright yellow jacket, as any intelligent person preparing himself for a possible firefight would do.
One of the parents Officer Hull was protecting can be observed in another Hicks photo. Again, this is a high resolution Shannon Hicks photo.
You can see what appears to be a woman hiding behind the dumpsters. We know from the report, two women hid behind a dumpster while an Officer protected them. This appears to match the report.
It is believed Officer Hull can be seen evacuating the parents in this portion of the video:
Officer's Hull's statement - doc #2101.
More details during a later publication..