2:58 PM PT -- Law enforcement sources tell TMZ ... Aaron seems to have lost control of his motorcycle after striking a curb in a roundabout.
Our sources say witnesses told cops they saw Aaron's 2018 Suzuki GSX-R750 traveling at a high rate of speed through the roundabout before the crash. We're told Aaron was wearing a helmet and no other vehicles or people were involved in the crash.
We're also told medics performed CPR on Aaron after other motorists had attempted chest compressions before first responders arrived.
Aaron Grissom -- best known for competing on Season 12 of 'Top Chef' -- is dead after an apparent motorcycle crash in Washington state.
Grissom died Tuesday after suffering "multiple blunt force injuries" in a traffic accident, according to the Pierce County medical examiner ... who ruled his death an accident.
According to a friend and former coworker, the wreck happened in the area of Chambers Bay.
Grissom was one of 16 contestants on "Top Chef: Boston" in 2014, though he wasn't much of a fan favorite, and got eliminated pretty early. While appearing on the show, he was actually a resident of L.A. and worked as a chef at North Hollywood's Bow & Truss.
Before that, he appeared in an episode of "Diners, Drive-Ins and Dives" when the show covered Dirty Oscar's Annex in Tacoma ... where Aaron made a name for himself.
According to reports, he had been working as a restaurant chef in the Tacoma area recently again, and was also cooking for touring singers, including Billie Eilish, before the pandemic shut things down.