Jack Reynor was chosen to play the brother because the filmmakers felt his mannerisms and voice reminded them of Bill Paxton, an actor the directors had wanted to work with but never had the chance to due to his unfortunate death in 2016.
The movie was based on a dream one of the directors had involving a young boy sitting in a run down mid-western hotel bathroom analyzing a futuristic weapon. This scene was later incorporated into the film.
The climax of the film involves a shootout in a police station, similarly to the iconic scene in The Terminator (1984). Elijah can be seen playing the arcade version of The Terminator 2 earlier in the film.