As the agents are evaluating the scene of the initial explosions, they estimate it would take 100 kilos (220 lbs) of Ammonium Nitrate to cause the damage. They later determine the suspect has skimmed an additional 200 kilos (440 lbs)of AN, and thus could make two more bombs. AN is only dangerous in such small quantities when mixed with metals such as tin and magnesium (the suppliers of which they make no effort to track down) and is set off by an additional, outside-sourced explosion.
Forrester requests U.S. military assistance and asks them to dispatch a "grizzly". The military uses the term grizzly for a number of different things, in this case it is referring to the radio callsign for the U.S. Navy's EA-18G Growler. The Growler is a carrier based electronic warfare aircraft, it is a specially modified version of the Boeing F/A-18F Super Hornet, it carries specialized equipment that allows it to monitor, intercept and/or jam radio and other wireless signals as well as radar.