The procedure was supposed to be a routine one at Yorkville Endoscopy.
Rivers stopped breathing and went into cardiac arrest before medical workers were called by 911.
According to reports, the doctor who performed the endoscopy -- Dr. Lawrence B. Cohen is a gastroenterologist -- had brought an ear, nose and throat specialist into the operating room to examine Rivers. That doctor was not authorized to perform procedures at the clinic.
Rivers died Sept. 4 after being taken off life support.