Two riders killed during AMA Pro Flat Track race at Sonoma County Fairgrounds

SANTA ROSA, Calif. (KGO) -- The motorcycle-racing world is mourning the loss of two promising young stars. Both died during a big race this past weekend at the Sonoma County Fairgrounds.

Twenty-year-old Charlotte Kainz of Wisconsin died Sunday, shortly after colliding with another racer. And 17-year old Kyle McGrane of Pennsylvania died Monday from injuries suffered during his crash on Sunday.

Their accidents came in separate races at the Santa Rosa Mile, the final event of the pro flat-track racing season. They ride on what's called a "cushion" surface, spewing dirt going sideways at more than 100-miles per hour.

McGrane, a high school senior who started riding motorcycles at age 3, crashed on the final lap of his race.

And Kainz, a rising star who had just won her first event earlier this year, crashed into another rider during her heat. That rider has minor injuries.

Race officials are reviewing what happened and their own response.

AMA Pro Flat Track has set up a memorial fund for Kainz and McGrane. Click here for the link. You can click on either racer and easily donate a set amount to help their families with expenses.