Cannot assume anything these days.  It's a long shot, but for all we know, maybe the lady just stabbed the guy with a very large knife and he pushed her in an attempt to get away.  The news media likes to omit facts or "embellish" when it best suits them.  

Absent justifiable self-defense, I can't think of any good reason why a 51 year old man would be beating on a 80 something woman.