The visit
It was a total shock when the aliens landed. Simultaneous landings in Bolivia and Senegal. No one, no scientist, no astronomer, no military leader from anywhere on the planet saw them coming, or had a single word of warning. Panic set in almost immediately. Strong nations sent delegations, military groups, and scientists to confirm and coordinate. They operated both in public and in secret. Incredulousness faded slowly, and many still had a hard time believing it was true, but the evidence stacked up. The Argentinian Prime Minister had fainted at the U.N. Video, which theoretically could have been faked, piled up in an manner that overwhelmed most conspiracy.
Aliens had landed, caused panic by merely existing, and humanity faced a shocking crisis about how to compose itself in regards to itself, each other, and the aliens.