No we don't know if anyone was sitting beside him, it's highly likely though. It's a truly bizarre event, it doesn't appear to have been under control right from the start. Looking at where it became airborne at 116kts is appears to have become airborne as a consequence of speed and configuration, never got above 160 feet, just a very shallow arc over 9 seconds to impact. It bares all the hallmarks of an incapacitation or pilot seat malfunction. There doesn't appear to have been any control inputs at all.