I read the who NYT article (too long to post the whole text here) in full. Biden called on Saturday. Trump didn't. I later read he called a few days later when all the news agencies had already pointed out that he didn't call immediately.
https://www.ndtv.com/world-news/not-trump-biden-dialled-widow-of-rally-shooting-victim-she-didnt-pick-up-6116808
Also, on that Saturday, Biden called Trump immediately the same day.