Apparetly the news spread by Jazztimes was wrong and Jack Sheldon is still alive :
Reports of Jack Sheldon's Death False
Earlier this morning we mistakenly published an obituary on Los
Angeles-based trumpeter Jack Sheldon, based on unconfirmed reports
from within the jazz industry that Sheldon had died.
Sheldon is not deceased. His wife, Dianne Sheldon, has confirmed that
Sheldon is alive and well and in Los Angeles. Mrs. Sheldon also said
that she does not know how the rumors began.
JT regrets the error."
TuneUp regrets the error as well. Long Live Jack Sheldon!!