Question
can a person die from c5 c6 injury

Answer
Absolutely!  Your question is pretty broad here.  What kind of injury are we talking about?  Decapitation at that level will definitely kill you! *smile*  Damage to the spinal cord at that level can kill you.  Disc injuries could really immobilize you, sprains can hurt you.

When you get down to it, humans are pretty fragile.  We are in this mad rush to destroy ourselves, as well, smoking, drinking, eating bad food and toxifying our environment.  It's amazing we survive each day, yet somehow most of us do.

Hope this answers your question.