A few minutes ago I learned that Jonathan Groves died on 4 June 2011 at the age of 29.
I learned this from this Editor's Note at the end of
Jonathan Groves, "An elementary counterexample in the compact-open topology", American Mathematical Monthly 119 #8 (October 2012), 693-694.
The Editor's Note follows:
Johnathan Groves passed away on June 4, 2011 at the age of 29 before this note was accepted. The Monthly thanks a colleague of Jonathan's, who wishes to remain anonymous, who saw the note through revisions and proofs. We extend our deepest condolences to Jonathan's family.
According the , Jonathan has 2068 archived posts in Math Forum. I can recall many of these being quite lengthy posts, and probably a large majority of his posts were made in the math-teach group. It appears that Jonathan begin posting in early February 2009 and his last post appears to have been made on 25 April 2011.