Leffler was participating in “Night of Wings,” a 25-lap event for sprint cars.
NASCAR released a statement:
NASCAR extends its thoughts and prayers and deepest sympathies to the family of Jason Leffler who passed away earlier this evening. For more than a decade, Jason was a fierce competitor in our sport and he will be missed.
Leffler ran nearly 300 Nationwide Series races in his career, earning two wins and more than 100 top 10s. He also ran about 70 Sprint Cup Series races, including the Party in the Poconos 400 at Pocono Raceway last week, finishing 43rd after having a transmission issue.
In 2003, Leffler was inducted into the National Midget Auto Racing Hall of Fame. He had 18 midget car wins at that time.
After news of Leffler’s death spread, several drivers offered their condolences.
— Kyle Busch (@KyleBusch) June 13, 2013 
Lost a good guy tonight in Jason Leffler. Prayers with your family!.
— Bobby Labonte (@Bobby_Labonte) June 13, 2013 
My thoughts and prayers are with Jason’s family and friends. Breaks my heart thinking of his little boy
— Jeff Burton (@RCR31JeffBurton) June 13, 2013