There are physical reasons for a face to look strange. One is a TIA or mini stroke. This causes the face to distort and look as if it is melting by sagging A LOT. This is of short duration and the face goes back to it's normal look after the event. Also, there are mental illnesses that can cause the face to manifest extreme distortions. Between fear of the observer and the event itself, you saw what you saw but the cause was most likely of a physical source.
I see. Thank you. You don't know exactly how much this information puts me at ease. Thank you so very much.