Regardless of risks of vigilante 'justice', I consider this sort of crowd-sourced investigation a highly valuable development. For the simple reason that there's a significant chance that this attack, like many others, was done by elements of the government. Or groups with the ability to strongly influence the official investigation.

The days when we the people could trust the motives or results of official investigations into politically significant crimes, are long gone.

The government develops ever-more powerful technological tools for monitoring ordinary people. It's entirely appropriate for ordinary people to use every technological tool at their disposal to guard against government wrongdoings.

If the Internet was able to identify the person(s) responsible here, and prove (for eg) that this was a government ploy to ban the sale of ammunition reloading black powder or bulk cartridge sales, that would be of immense significance.

For this reason I applaud the posting and permanent archiving of photos of events where such attacks occurred. We need some way to bypass the controlled MSM's low bandwidth and tendency to publish low-res, selected, edited and generally useless news images. 4chan doesn't cut it, due to the impermanence problem.

Another thing to be wary of, is the 'vanishing 911 photos' syndrome. Some organization appears, solicits the donation of original photo/film media with the promise of building a public archive, gets given a vast amount of such material, then vanishes along with all the material. NEVER give away or sell your original material. Post copies!