Sure, they used violence. As I said, the first time the elections wasn't any special compared to others in the Weimar republic. And sure, violent people and organizations only become more violent the power they have and the more shit they get away with.

The true violence campaign happened during the second election so. Which is the reason this election isn't considered legitimate anymore. And 30 % would make them a contender to form a coalition government in modern day Germany, just for perspective.