The cover of the very first issue of USA Today mentioned the death of two authors, one known for writing thrillers, the other best known for a more famous sibling. Who were the two authors and how did each die ?

The only two authors I could find that died in that era were John C Gardner and Frederic Dannay.

PS: Dame Edith Ngaio Marsh from England died earlier that year I beleive.

John Gardner is correct, having died in a motorcycle accident. The other, a bit tougher, was Leicester Hemingway (yes, brother of Ernest), who like his brother chose suicide.

Thanks for the answer !