# Is it possible to double crit? [duplicate]

My question is related to rogue archetype assassin. On surprise rounds if I hit a creature it is automatically a critical hit. But what if I rolled a natural 20 on attack during surprise round? Does that count as double critical hit?

I'm asking this because on lv 17 assassin gets Death Strike that doubles the damage dealt when you attack and hit a creature that is surprised, it must make a Constitution saving throw (DC 8 + your Dexterity modifier + your proficiency bonus). On a failed save, double the damage of your attack against the creature. So that is damage rolled x4 by the rules, so if you roll a nat 20 on a surprise attack does that make it x6?