Although the most intense scene in the film, the flashback that Davis has with his father mistreating his mother was one of the most fun to shoot. Not because of the content of it, but because Michael Conley (the actor portraying the father) was so out of his comfort zone playing such an intense role. Being more of a comedian, he would randomly start cracking up while shooting, which would result in the entire crew bursting into laughter as well.
Micaiah originally had this story as a short film set at Christmas time and would include a young man thrown out of his house by his parents and contemplating suicide, with a few other differences. But when Christmas came and went, he still wanted to use the premise for a film. So he changed the story a bit, added some more characters and elements, and Purpose was created.
It wasn't originally set in the script for the last scene to take place during a snowfall, but when it came time to shoot the scene and snow was falling, Micaiah thought that it would be the best way to do the scene, considering it was a wonderful contrast to the gray setting from the rest of the film.