They did. The ending was intended to say "Reeves shot himself."
My description may be a little off since it's been over a year since I saw it but as I recall, throughout the film we saw different people's different versions of what they claimed or thought happened to Reeves when he went upstairs and to the bedroom. In each of those scenes, Reeves looked the way he did in all the flashbacks: fairly young (younger than Reeves was, in fact) and still glamorous.
But in the last version of that scene we saw, at the end of movie, Reeve looked older and fatter than Affleck did in the rest of the movie (even in the other versions of the bedroom scene). He was tired, drunk and clearly depressed. The implication sure seemed to be "This is is the 'real' version."
And, in that version, the 'answer' was "he shot himself."
