Unless I'm missing some obscure website out there, absolutely no one imagined what turned out to be the case: that the violence was unleashed by two young immigrants with Chechen backgrounds. Chechnya was not on anybody's radar screen - and it does not appear that the conflict in that rebellious Russian republic actually had much to do with the actions of Tamerlan and Dzhokhar Tsarnaev that day.
We then moved, with dispatch and without pausing for more information, to show how the event proved that our side was right in any number of ongoing debates.
Opponents of immigration reform used the fact that the brothers are immigrants as a lever to derail the rapidly forming consensus in favor of broad repairs to the system. Supporters countered, defensively, that if there is any lesson here, it's that our approach to immigration needs to be modernized. In truth, this horrifying episode has little to do with immigration reform one way or the other.
We fell back to other familiar ground. Sen. Lindsey Graham (R-SC) said we should assume these brothers had to be linked with one of our international enemies and that Dzhokhar should therefore be tried by a military tribunal and not in a normal American court, the venue to which his status as an American citizen entitles him.
The Obama administration doesn't get credit for much these days, so it deserves courage points for deciding that Dzhokhar be treated in a way that protects the rights of all other citizens.
And, of course, what I have just written means that I cannot claim to be immune from the very forces I'm describing. My own passion for saner gun laws similarly led me to ask why we have not focused more on how the brothers obtained their weapons or why it was so hard (because of the NRA's opposition to chemical "taggants" in gunpowder) to trace where they got the material to build their bombs.