I learned about Apostol's death from a post by a very astute mathematical biologist, Lior Pachter, who was once a student of Apostol's. The post is "The Ice Cream Cone Proof,"[1] which nicely illustrates Apostol's brilliance as a teacher.

[1] https://liorpachter.wordpress.com/2016/05/09/the-ice-cream-c...