22-year-old Mariella Medina was getting home from the gym Monday night near Dallas, and saw smoke and flames down the street.

She ran toward the site while she called 911. It turned out someone's shed went up and the fire was spreading to the house. Then Mariella saw a woman standing outside with three kids, but her seven-year-old son was still inside.

Mariella told 911 what was happening, the dispatcher told her not to go in because it was too dangerous. Well, she immediately ignored that advice, ran into the house anyway, made it upstairs, found the kid in his bedroom, and got him out in time.

She says she'd never even met the family before. "The main priority is getting someone out. You don't have to know somebody to want to help them," Mariella said.

Luckily the fire department put the fire out before the whole house went up, so they'll be able to rebuild.

Read more at NBCDFW.