Shawn Tompkins cause of death was heart attack

That's according to Sam Stout, brother-in-law of the famed mixed martial arts trainer, who spoke to the London Free Press about Tompkins' untimely death in Ingersoll back on Aug. 14, 2011.
From "Hands of Stone:"

"I don't know what to say. It's not supposed to be happen to a healthy 37-year-old person. Who would think he had to get checked out for that?"

Tompkins autopsy was performed yesterday (Aug. 13) in London, Ontario, Canada, however; the official results have not been released.
The Canadian combat guru got his start as assistant -- and eventual head coach -- of the Los Angeles Anacondas under the International Fight League (IFL) banner back in 2007.

Tompkins would spend two years as a trainer at Xtreme Couture before migrating to the TapouT Training Facility in late 2009 and is perhaps best known for working with UFC fighters Chris Horodecki, Mark Hominick, Vitor Belfort and Wanderlei Silva, among others.

Fans who wish to contribute to The Shawn Tompkins Memorial Fund, designed to assist his wife Emilie with funeral costs, can do so through the AMR Group by Emailing TeamTompkins@ShogunMMA.com.

In addition, a memorial guestbook has been posted for fans who wish to express their sympathies to Tompkins family here.