Speaking of knowing what you're talking about. . .

Now here's an interesting (paper on a) study.

Here is the actual study.

The important information (for us writers) is this:

"When thinking about a positive past event, people should be happier when they describe it using the imperfective aspect (which brings them mentally closer to it) than when using the perfective aspect.  When thinking about a negative past event, people should be sadder when they describe it using the imperfective aspect (which brings them mentally nearer to it) than when using the perfective aspect."

That is--if you want to make someone feel a past emotion (or event) more keenly, use the imperfect (he was dying). If you want that to be more distant, use the perfect (he died).

Not that we don't "know" this intuitively--but we don't always create what we intuit and it's important to know from a neurological standpoint why we should make certain decisions as a writer.

Also, think about what Meursault would have been like had he said "mother was dying yesterday" instead of "mother died today." Whole different ballgame, I think.