I doubt this was set up by any organization. However, I do believe a mentally disturbed and vulnerable person was influenced by rhetoric and hysteria.
When people are making trumped up or false claims about the dangers facing a community there is an opening for those that are susceptible to act upon their paranoia.
Blame is difficult to assign here. Obviously, if the man is mentally ill, then the system failed at identifying him and helping him with is condition. Further, incidents like this one should hopefully teach partisans on any side to mind the sensationalism and hyperbole. If you speak intelligently on the issues you care about, it usually goes over the heads of crazies. Instead, we are seeing how political groups have taken to pulling on peoples' most basic feelings and prejudices. While effective, at first, it often leaves people with buyer's remorse (agreeing something out of emotion and then later disagreeing after some thought) and leaves a negative and often hostile rhetoric that easily motivates people with certain issues.
Of course, scaring people into believing their livelihoods are in danger will continue to turn votes, so don't expect this to change any time soon.