I agree the victim was probable pinned at knee level for the initial trauma. However according to the article, bystanders were able to push the car back and the

I agree the victim was probable pinned at knee level for the initial trauma. However according to the article, bystanders were able to push the car back and then it rolled forward again pinning the victim a second time. Given that he had just (probably) had his knees injured, it's possible he was much lower to the ground during the second impact: if he were sitting or crouching, then he could have suffered pelvic, abdominal, or thoracic injury, all of which are life threatening. Anyway, all of this is speculation without confirmed details. (Edit: typos.)