Officials on the scene said the vehicle struck the back of a work crew's truck, which was parked on the side of the highway. Two workers who were standing behind the truck jumped out of the way to avoid getting hit.
Rylyn, who was originally said to be 3 years old, was taken to the hospital, where he died seven hours later, said Tulsa police officer Jillian Roberson.
Police are still investigating and tested Lewis' blood. Police haven't issued any tickets at this time.
Heather has a cut lip, swollen leg and bruises on her chest.
She donated Rylyn's organs.
"My son would not have wanted to live as a vegetable. I wouldn't want to put him through that. This way he can help other children," Lewis said.