What happens when lightning strikes us? How is it fatal?
Minor shocks definitely can paralyze a part!  Get on youtube and watch videos of people who cant let go of electrical wires or who are hit by tasers.

Paralyzing a part does not kill you.  Lightning can kill in two ways.


Arrhythmia.  Having arrhythmia or asystole is what kills most people hit by lighting.  As regards lesser shocks - the handymen who are hanging on to a live wire and can't let go (because their hands clamp down) can stay that way for a while.  Eventually the current produces an arrhythmia in the heart and that is what causes death.  If someone goes down this way from lighting or a lesser shock, you might be able to get them back with CPR.  


When you see a whole herd of animals killed by a single strike, that is why. The heart is sensitive.  I do not understand why people's hearts do not similarly stop when they are hit with tasers.  I think sometimes they do.  


Resistive heating.  Lightning can burn you.  Mostly the electricity goes over your skin and concentrated at conductors, like your phone.  That hurts but won't kill you.  Lightning going thru you can burn you on the inside which can damage your organs.  That is rare.    


https://www.cdc.gov/mmwr/preview/mmwrhtml/00052833.htm
https://en.wikipedia.org/wiki/Lightning_strike