Your post triggered a thought.
Maybe the [19] are a group or individuals on EITHER side who would be destroyed if harm should come to certain people.
Think nuclear standoff? MAD. Mutually Assured Destruction. the [19] could be good or bad guys in this case. Hostages of a sort. Like when the Corleones sent some guys over to play cards when Michael met with "The Turk" Solozzo. Guarantors of safety.
See what I'm saying? Not sure if this is an original thought or commonly understood by everybody. Thinking outloud I suppose. The "nuclear standoff" phrase did baffle me a bit.
that is possible. I was leaning towards they overlap different agencies and will take out the others in an attempt to save themselves.