Prince George's County officials said firefighters with the Branchville Volunteer Fire Company were called to a school bus fire in College Park around 4:45 p.m. Monday.
Dashcam footage released by fire officials showed flames erupting inside the bus as thick, black smoke poured out of the vehicle.
Bus driver Renita Smith said she had just made her third or fourth stop when the dashboard of the bus began beeping.
Then, she smelled smoke. With a look into her side mirror, she saw flames.
With no time to think, she stopped the bus.
"I put the mic back down, undid my seat belt, jumped up, got my babies and got off," she told ABC News. "Once we got off, neighbors kicked right into 'Mommy mode,' as I call it, and helped the kids get to a safe haven. When that was going on, I ran back onto the bus to make sure there was no children on the bus...By the time I got to the last step on the bus, it just went up in smoke."
Smith was able to get the 20 children - ages 4 to 9 - off the bus and to safety just before fire engulfed the vehicle.
After saving them, she went back into the flaming bus one last time to make sure no one was left behind.
None of the children were injured, thanks to Smith. Most of the children were picked up at the scene of the blaze by their parents.
Smith, a mom of two, said her reward was getting the children safely to their parents.
"When I'm driving them, you're my children until I drop you off to your biological parents. I have to handle each child with care, as a mommy would her own, so that's what I did," she said. "That's what I hope any human being would do for any child."
Firefighters believe defective brakes were the cause of the blaze.
ABC News contributed to this report.