I seriously doubt that the video is what caused this guy to act. It’s not like he was fine until yesterday evening right after he watched the 6 o’clock news.
John Douglas, founder of the FBI's profiling unit, has articulated the importance of "stressors" as principle elements of serial criminal behavior by psychopaths. Stressors, which serve to trigger the criminal behavior, can be very obscure and unpredictable for different individuals, but my point is this guy or any number of others may have had deeply rooted problems for years or decades, but just seeing another nut job get his 15 minutes could very well be enough to prompt them to act out their fantasies.
I am sure that you are correct. However, the coverage does have potentially terrible consequences. This Cho idiot admits being influenced by the Columbine losers. Were the coverage of that event less extensive, at least that aggravating factor would have been removed.