I'm afraid nothing can be done. This is what happens when we fear something so much that we can't even have a conversation about it, when we refuse to do anything and allow fear to control the discussion - irrational fear of what pot does, and the cowardly fear of being demagogued as being soft on pot and on (the overextended catch-all phrase) "drugs" by people seeking political advantage. When we demand the use of unlimited force against things that we don't understand, then we suffer. Superstition ain't the way.
So, unless we allow ourselves as a country to acknowledge that marijuana is not evil, and is not worth committing violence over, this kind of thing will continue to happen, 40,000 times a year. But we won't acknowledge that. We are cowards.