While I partly agree, I remember examples such as the terrorist attacks in Paris where it was covered on every media for a long period in time, and a few months later there was a mass killing in Afghanistan with way more deaths and obviously was done in the same dramatic way but most media didn't even cover it.
I'd say it has to do with how unexpected is that event to happen. Same applies to people's grief. Everyone had some sort of support for paris up, or even with the newspaper attack ze suis etc, noone cared about what happened in Afghanistan. :/
