Because of the especially heinous nature of this crime (innocent young children gunned down—if he had to get back at someone for his shitty life, why not kill the actual people who had teased him in high school?) I think this will have more lasting impact than previous massacres.
(1) There will be new momentum to get gun control legislation passed. (This is not an endorsement, merely a prediction. I write this to ward of hate comments. For some weird reason, HBD blogs attract a lot of pro-gun people. Even though belief in HBD should mean understanding that there are a lot of people out there whom you shouldn’t feel comfortable with them owning guns.)
(2) Backlash against aspergery people.
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Commenter SFG answers the question of why people who read HBD blogs are pro-gun:
It's pretty simple. You're on Team Blue, or Team Red. (There are smaller teams, like Team Yellow for the libertarians, and Team White (or Brown?) for the WN people.) If you join a team, you start believing all the other stuff the people on that team believe, because you get your news from sources on that team, and you don't have time to evaluate each and every proposition on its merits. So HBD people are on Team Red (or White) and tend to be pro-gun for that reason--they're always reading articles about how gun control isn't really the answer on the conservative sites they frequent. Similarly, liberals, who I presume you agree with on abortion, etc., tend to be wrong about race because they're always reading about how it doesn't really exist, etc. on the liberal sites they frequent.
Plus there's the affiliative drive, or herd instinct. Even people who claim they have no herd instinct tend to find a virtual herd like libertarians, anarchists, or far-left hippies, and agree with those people.