"I came over, I tended to her right away because she was very, very scared and nervous," said witness Angela Sephton.
"She just kept crying and crying saying I can't feel my legs, I can't feel my legs. I just concentrated on her and said just relax, look at me, focus on me, just take some deep breaths," she said.
Sephton said the teenage girl was celebrating her birthday Friday.
The girl was airlifted to Children's Hospital of Los Angeles. A ground ambulance took the boy to the same hospital.
Victory Boulevard was closed for a time to allow a city fire helicopter to land.
The driver of the van that was hit was trapped and had to be freed.
Police say the woman driving the car that apparently triggered the crash was not seriously hurt. Officers said it's not clear what charges she might be facing.
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