Mechanic: The structure of the charge is what causes it to be 'shaped' (but you know this). If the mixture was set-up, that is, firm enough to be molded, so the back of it was flat against one wall of the van and the side toward the building was 'V' shaped so the legs of the 'V' faced toward the building you would have a charge properly shaped to cause that type of destruction.
I do not recall the exact time of the detonation but you can bet that if it was earlier in the morning none of the feds would have been in their offices - coffee and donuts first ya know.
Instilling fear in the population is typical of government agencies - how else can they justify their existence, and the sacrifice of lives to build public support is not a uncommon tactic governments.
And what greater sacrifice do we offer up to the gods of social protection than those of our innocent women and children. As for the fbi not being there when the bomb went off - either it went off before they normally got to the building (but then you have to wonder if they close up shop at 5:00 pm every day and re-open only at 9:00 am the next day) or they knew something was up and just kept it to themselves (typical of intelligence types to be smarter than anyone else and not believeing anything until it actually happens); but as with any sacrifice, people do not object as strongly to police, etc., being killed as they object to the loss of innocent lives. This situation still stinks worse than a open sewer pit. jmtcw.