Will be interested to read the NTSB accident report. It's either pilot error or mechanical failure. Guessing they will call the first option since I haven't heard of any reports of a mayday call. That doesn't mean no call means they didn't have a mechanical failure. We were always taught "aviate, navigate, communicate." Whatever happens, fly the aircraft first! Next, head to your destination or the nearest safe place to land. Third, and lowest priority, talk.