Fitness trainer Eric Fleishman, a celebrity trainer known as “Eric The Trainer,” reportedly died “unexpectedly” on Thanksgiving Day at his home in Glendale, California.

The fitness expert was only 53, according to TMZ Sports.

The fitness guru’s cause of death is not yet available.

Fleishman worked with several stars, including Kirstie Alley, Patrick Schwarzenegger, Ethan Suplee, and Jason Priestley, as well as musicians from bands including Def Leppard, Journey, Fall Out Boy, Nickelback, and more.

The trainer also worked closely with members of California’s law enforcement community during his 30-year career. He worked with the California Highway Patrol and SWAT organizations across the country.

Fleishman leaves behind his wife, Alysia, and son, Henry.

Several celebrities mourned Fleishman’s passing, including actor Martin Kove, who is currently starring in the re-boot of the Karate Kid franchise.

Others also offered their shocked condolences:

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