Complex, obscure, figure it out on your own, left hanging ending, flashbacks are all cute, but not when added together and shows a deep disregard for the variety of viewing public's desires & capabilities.
That said, you get a killer (we are given no reasonable reason why) of a couple of strangers (one of whom also has an untold hinted at background), and possibly a third victim also with an untold hinted at background. Lots of film time spent on looking at a car on a snowy road, a watch & a key set (Why? Who knows.); telling a story of our killer as a child, and film time suggesting a body lies under a tarp in the basement; frame by frame views you don't see any evidence of that.
That said, you get a killer (we are given no reasonable reason why) of a couple of strangers (one of whom also has an untold hinted at background), and possibly a third victim also with an untold hinted at background. Lots of film time spent on looking at a car on a snowy road, a watch & a key set (Why? Who knows.); telling a story of our killer as a child, and film time suggesting a body lies under a tarp in the basement; frame by frame views you don't see any evidence of that.