An Iowa boy who asked for racing stickers for his casket died early Monday morning after a battle with leukemia, family members have said.

His stepmother, Kylee Hammond, posted a photo of him on Facebook in a race car driver uniform with the years "2007-2018" underneath.

Caleb Hammond, 11, of Oskaloosa, Iowa, was diagnosed with leukemia when he was 9 at Blank Children's Hospital in Des Moines. After getting a bone marrow transplant in January, the cancer came back aggressively and he and his family decided to end treatment and return home so he could go out and enjoy his last days.

More:An 11-year-old boy dying from leukemia got wish: Race stickers for casket

One of Caleb's wishes was for people to send him racing stickers to cover his casket. The response was so overwhelming that he even got a chance to drive a race car on a track.

"Our little Mr went peacefully in his sleep at 2:00 a.m. today surrounded by our families," wrote Holly Kempf, Caleb's mother, on Facebook. "Before I was woken up being told he was getting ready to pass, he was smiling at me while I was dreaming. With my hand on his chest, I felt his last breath and a few last heart beats."

Caleb's story has resonated with people across the country. On Monday, 12 NASCAR entries will sport #TeamCaleb stickers on their cars at the Indianapolis Motor Speedway, according to ESPN.

Laura Mulder met Caleb during a racing event that was held for him in Oskaloosa in August. Since then, she's been speaking with his mother and stepmother and following his journey.

"He will be in my heart forever," Mulder said on Monday. "That smile and those eyes forever. They will be with me forever."