Getting rid of guns in any method we have available to us would largely just strip them from well-meaning citizens. They're too ingrained in our culture and economy; it's impossible to get them out of the hands of organized crime and even unorganized criminals. I do also question how they obtained them, though. I think that would provide some important context on that particular discussion. I applaud the authorities for being on top of this, though.
As far as the two guys themselves go, I don't know anything about them other than their attempted actions. I don't know what to say as far as a solution. Were they sick? Were they just bastards? I don't know. How do you fix that? Can you even fix that? I don't know. I don't think any suggestions I have would be particularly well-informed or useful, especially without knowing anything about who these two people are. Best to leave it to people who spend their lives researching these things, if you ask me. If it bothers you that much, dedicate yourself to becoming one of these people.