What would happen if the moon lost 100% of its orbital velocity?

Consider that a meteor about 6 miles across colliding with the Earth wiped out about 70% of all the species on the planet (the dinosaurs were not the only casualties). Think about what a meteor 2160 miles across with about 1/6 the mass of Earth would do. There aren't going to be any survivors of any kind. Such a collision would probably liquefy most of the planet and send large amounts of shrapnel into space. It wouldn't be pretty.