Yeah this happened today in my small hick town, georgetown, texas. so far i havent seen and fbi agents around town yet though.

Whilst this nay sound alarming, it is commonly available in fertilizer as previously stated. The fact that it was in pure form only means that a terrorist would need about 900lbs of generic fertilizer (for the same amount, a good bomb making fertilizer has about 30% ammonium nitrate.
Ammonium nitrate has to be mixed with fuel-oil ( about 96%ammonium nitrate 4% fuel ) and then set of with a high order explosive ( TNT,PETN,RDX etc ). A blasting cap just won't do.
I believe the Oklahoma city bombing was a 2 ton fertilizer bomb. So they are powerful, but not as much as military explosives.