Our friends at Insight Crime have posted background and some details here.
From worried individuals on the ground and some bomb expert sources in Monterrey and the US, we've learned the following:
1. The bomb was most likely not C-4 but a combination of Amonium Nitrate and Tovex.
2. The bomb might have been a reprisal from the Gulf Cartel, responding to the decision of a mid-level commander in Guadalupe who did not accept a bribe (approximated at US$250,000 to look the other way)
3. The clock is ticking on whether or not we'll see another bomb. In short, most agree that a second bomb detonated by the end of the day today would strongly indicate a protracted campaign
4. If there is a campaign, it will not take more than two or three bombs total to change the landscape of how the military operates in Monterrey moving forward
5. This change could significantly complicate communications as well as patrol planning and logistics.
6. The psychological impact of a two/three bomb campaign at this point are immeasurable - a testimony to how effective bombs can be.
7. And finally, the consensus among a limited few, well informed individuals runs against common notion: Los Zetas are not the most sophisticated bomb makers in Mexico. As one source said, "Los Z are more often attributed to pipe bombs and other relatively amateur stuff. This most recent bombing looks something more like what the Gulf Cartel has pulled off in the past. Targeted, relatively more sophisticated construction, and remote detonated."
One last thought: Mx. authorities snatched a bundle of C-4 recently in Jalisco. The stuff is out there… It reminds me of a conversation I had with ATF friends in early 2009, when we were talking about escalation, and their worry for IEDs in Mexico. We haven't reached the levels of Iraq, for example, but the current climate appears to be heading more in that direction than not.