The account seems somewhat dramatic, agreed. However, if the "broken leg" involved the femoral artery and "internal injuries" involved unspecified vital organs, then it's not hard to understand that he expired without immediate care.
Having lived in earthquake prone areas for many years, I will acknowledge they are the most sudden and sinister of all natural disasters. Why he felt the need to "jump," if true, is something I don't quite understand. May the good man rest in peace, in any case.