You may go to your local INS office with I-485/I-131 receipt & the evindence of emergency ( as the diagnosis of doctor in China ),if your father's situation isn't good,you may get AP at same day.Usually you need to wait a few hours.By the way,if any document(s) are Chinese,your need to translate to English. You're better to write a letter to INS to explain why do you need to go back as soon as possible.