How about this:
Dutch is retired and lives alone, he has nothing good left to look forward to in life. But he gets a knock on the door and it's two members of the military and they inform him that a huge group of "Aliens" have attacked and they match his description of the "Alien" he had seen before. And they say that they are always on the move on a rampage, killing and destroying everything in sight, cities, small houses on the countryside, and beaches. As if they are trying show some sort of power. (They are really trying to show humans what they are made of due to their fallen comrades that have happened during hunts). Dutch thinks about the offer and if he's fit for job because of his age, he then thinks of what he actually has to look forward to in life, he accepts the military's offer and they introduce him to his new team and they go out to "Hunt" the hunters.