The leftists are desperate for a mass murderer to be from one of their despised target groups - TEA party, GOP, conservative, Christian - and their MO is to immediately gloat following any mass killing in their hope that the perp is from one or more of those groups. They project their sick hatred onto these groups in sick hopes that they’ll have something concrete to justify their hatred. So, for a brief period following a mass murder, they are pleased with themselves, knowing, I suspect, that the giddiness will be short-lived.
For any honest psychiatrist, this mindset would be a target rich environment of analysis.
Last I heard, some guy named Diogenes was still looking for one...