Tompkins was 37 years old and is survived by his wife Emilie Stout, the sister of his fighter Sam Stout.
Josh Gross spoke to Emilie:
"Unfortunately I'm in Las Vegas and he's in Canada," she said. "I'm hearing through my family and his family that he didn't wake up this morning. They're going to do an autopsy tomorrow, so we don't know any of the actual details. But from what we do know, he passed away in his sleep."
MMA Junkie had more:
Veteran lightweight John Gunderson today told MMAjunkie.com that Tompkins "didn't wake up," but he was still unclear on the details surrounding his passing.
Longtime friend and confidant Chris Horodecki said the trainer was in Canada and had spoken to him yesterday but was unaware of the bad news when contacted today.
Tompkins had an 0-4 MMA record but had fought extensively as a professional kickboxer and Muay Thai fighter. Tompkins was credited as a co-author of Erich Krauss' The Ultimate Mixed Martial Artist: The Fighter's Manual to Striking Combinations, Takedowns, the Clinch and Cage Tactics.
He will be remembered for his impact on the technical aspects of MMA striking and the victories of his students.