MMA trainer Shawn Tompkins dies

Shawn Tompkins, a mixed martial arts trainer known for guiding the careers of several accomplished fighters, passed away Sunday in Canada. The cause of his death is unknown. Tompkins was 37 years old.

Tompkins is survived by his wife, Emilie, who confirmed her husband's death late Sunday night.

"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."

The office of the chief coroner for Ontario confirmed it is conducting an investigation into Tompkins' death.

Tompkins was known for molding young fighters like Sam Stout, Mark Hominick and Chris Horodecki into crisp, technical strikers. He started with Stout when the lightweight was just 16. Stout became Tompkins' brother-in-law after the trainer married Emilie. The couple moved to Las Vegas from London, Ontario, Canada, in 2007.

Tompkins' mentor Bas Rutten, a former UFC heavyweight champion, told ESPN.com he spoke to his friend on Saturday evening.

"Shawn is one of my best friends, one of the best if not the best striking coaches on the planet, and I mean this," said Rutten, who made the blond-haired Canadian the head coach of an International Fight League team in 2007. "He always put his students and friends before him, would do anything for them."

"He texted me late last night, telling me he loved me," Rutten said, "so thank God I called him to tell him it was mutual."

Beyond Tompkins' roll as a trainer, he established an almost paternal roll with many of his fighters and was fond of calling them "son." After relocating to Las Vegas, Tompkins settled at Xtreme Couture until he moved on to become head coach at the TapouT Research and Development Training Center in 2009.

Earlier this year, Tompkins ran Hominick's corner during a UFC featherweight championship fight in Toronto. This was the closest Tompkins came to earning his stripes as a UFC championship trainer. Hominick fought valiantly but dropped the fight on points to Jose Aldo.

Tompkins fought before excelling as a trainer, losing each of his four bouts in the Montreal-based promotion UCC.

Tompkins was in Canada to help prepare Horodecki for his next bout on Sept. 10.

The trainer's remains were moved to University Hospital in London, Ontario, where a funeral service will be held at 1 p.m. ET Friday at West Park Church.

"Obviously I think he was an amazing man," Emilie said, "and I hope everyone shares their good stories about him."

Josh Gross covers mixed martial arts for ESPN.com.