You beat me to it.
I have my own personal theory as to why OKC was a government op, but before I state it...
...for those that are not familiar with these local news reports that were aired in OKC in the immediate aftermath of the bombing, check it out:
(but before you do, remember the official story: a bomb made of fertilizer and fuel oil, in a parked yellow Ryder truck on the sidewalk, caused all the damage)
(Edit: And before any doubters try to say that these were simple reporting errors, note the exact words. They're not speculating that there
might have been other bombs. They say that the FBI/Justice dept had
confirmed that there were extra explosives INSIDE the building.)