TOUTLE, Wash. -- A six-year-old girl helped protect her little brother when the van they were in began rolling backwards toward a cliff near their Toutle home.

The van was parked in the driveway of the kids’ family home and their mom had just run inside to put the newspaper in the house.

In the mere moments that she was gone, the van somehow started rolling backwards and little Katherine Whitman took action. She unbuckled her seat belt and moved to the driver’s seat.

 Slideshow: Children survive van plunge

“She says she tried to turn the wheel so it would go this way into the field. But she said it just kept right on going this way," Katherine’s mom, Sue Whitman told KGW. “Then, she jumped back in her car seat, put her seatbelt back on, took the blanket that was in the back and threw it over her and her brother to protect them from any glass.”

And by that time, Sue said the van was already about 50 feet down a hill located right next to the South Toutle River.

Once it stopped moving, Katherine climbed out of the van and grabbed onto branches and bushes to pull her way up the embankment.

"She came whipping into the house and said, ‘mama there was an accident,’" Sue recalled. “So I came out -- no van!"

Then, Sue ran to the edge of the cliff and a neighbor climbed down to rescue 18-month old Kurtis, who didn’t have a single scratch on him, thanks to his hero sister.

“All I could see was headlights and the front of the van,” Sue said.

No one was sure how or why the van started rolling backwards but Sue said she suspected that it may have popped out of park and into neutral when she shut her door.

Whatever the reason, it haunts her.

"I'm still crying at night,” Sue said. “I didn't sleep hardly at all last night. All I can think of is how lucky I am to have such a smart little girl to do what she did."

The van is back in the driveway now, fresh dents and all.

(KGW reporter Jack Penning also contributed to this article.)