I think it has much less to do with any particular murder, and is actually related to the rise of cable news that needed to find some way to fill an entire day,

I think it has much less to do with any particular murder, and is actually related to the rise of cable news that needed to find some way to fill an entire day, every day of the week, with national news. There just isn't that much national news, not the sort that keeps people tuning in. So instead they started taking local news stories that had some sensational elements and presenting them as national news stories. Stories about serial killers, kids getting hurt, etc.