it did appear that media coverage inspired Columbine to some degree- however many people started emphasising in the media what losers the people were who did it- not just before the attacks but the gratitude for their incompetence in executing the attacks. The result was that mass shootings seemed to go away for a while.
Columbine was also very thoroughly planned, as were a number of other incidents before- the difference is that every other incident they planned to die and did die. Whether the current perpetrator planned to die or not is uncertain, but if so he certainly did not follow through on it.
In previous cases people were also striking out at what they appeared to percieve as the source of their pain- the school where they were bullied or teased, the work where they felt dehumanized; this one seems to have been much more impersonally orchestrated- he was going for numbers rather people, it quite literally didn't matter who he killed. in this was he was acting much more like a psychopath than previous killing sprees did. it is interesting as well that he was a neurology major who was dropping out- I have to wonder if he didn't discover something about himself in his studies which led him to this act in some strange way. For example having a brain scan demonstrate that he was in fact a psychopath with an incomplete understanding of what that meant. Or maybe wondering if he could use such a biological defense to get off from a crime such as this.
On the other hand the booby trapping of his apartment and subsequent change of heart may indicate that he left the booby traps as a sort of revenge plan in case he did not survive...
As for prior to Columbine:
I count 6 mass shootings in teh 2 *years* prior to Columbine, which is where this record more or less stops, though I recall hearing about dozens of others durring the early 1990's and into teh 1980's as I was in college and high school
plots them out, you can see an increase in shootings leading up to Columbine, then a decline, a long lull, and now another buildup.
Interestingly this used to be known in China as "running Amok" and apparently happened (with different weapons- largely melee weapons) durring the British occupation. I suspect that Fox news trying to scare people while challenging the administration's legitimacy has more to do with the attack frequency than batman...