This is a terrorist attack. A major attack. We Americans are outraged and demand retaliation for this act. But, these (things, animals, monsters) do not use conventional methods that are associated with war. They have supporters who denouce them, so attacking 'hideouts' in countries would be well....... politically difficult. Their bases are in the middle of 'civilan' areas (ie an appartment on the first floor of a building full of kids thing).
Getting back at them will require using unconventinal mean. Maybe a SEAL team could work, but we have to take them out one by one. Sending in the 'fleet' may work, but they'll have too much notice to run. It has to be more covert, like the things the CIA do (if they still have their touch).
If this is war, then there are no trials. Target their 'generals' (ie money people and planners). But we must get them all.... or we'll be seeing more of their handy work.
They tried once to destroy the Wold Trade Center, but this time they finished the job.... unfortunatly.