It seems that the Ohio gunman claimed to be rather left leaning and wanted sen. Warren to be next president. Probably he hasn't read 8chan but still started shooting. He also claimed to be pro-Satan leftist, whatever it can possibly mean. So, I would say, that both he and large majority of public place murderers, serial killers, etc. are simply very sick people and presence of lack of presence of some random internet site does not make much difference.