The military has developed an AI computer to monitor all communications (including cell phones (which they can turn on the mic even if the phone is off), all networked video cameras (traffic, building security, etc), email, all purchases, etc). It decides that the current executive branch of the government is not following the Constitution and begins an operation to remove the branch and install a new set of leaders. The way it will do this is really stupid - using a brand new high tech explosive crystal to take all the targets out at a performance of school children playing instruments at a special event at Washington DC.
Given what this AI computer can do (think a cross between the computer AI in "I, Robot" and Skynet from the Terminator series, I guess), why kill them in such a convoluted manner? This computer can take over just about any piece of military equipment, traffic lights, cell phones, power transmission lines, trains, any computer, TV broadcasts, you name it. It kills people with auto accidents, missles launched from Predator vehicles, ejects pilots from airplanes, takes over junkyard machinery and wipes out some pursuit vehicles, etc.
To fulfill this mission it has this crystal shipped to a jewler to make a necklace out of so when the lady's son hits a certain note in the performance mentioned above it will set off the sonic trigger they embedded in his trumpet.
Really. Apparently that is the best they can come up with.
It couldn't just take out a couple of vehicles transporting these folks with a missle or something????
They also have the main characters steal an attache case from an armored guard unit and carry it around for a good chunk of the movie when all it is is a serum to slow their heartbeat so they can get in a shipping container on a plane. This computer can take over shipping computers for the newest top secret explosive crystals and the associated sonic triggers but can't have this serum waiting for them somewhere or shipped to them as well? Just dumb.
OK, there were other things, too, but these are a couple of the biggies.