I think first because we’re getting numb to violence in society - not just on TV, but in the real world. Second, because it brings up uncomfortable questions about health care, especially mental health care and it’s a white guy committing the crime, so it’s downplayed in favor of events that conform to the narrative of where the real danger in society lies - with scary brown people, not American born white guys.
There is a whole ideology underpinning how we talk about crime and violence in America, that unfortunately, wants us to ignore who is in power and how they’ve historically kept power, here in the US and how they expanded it abroad. The media is utterly complicit in this, which is why they tend to ignore or downplay stories that do not fit the current narrative that gives us a reason for waging war in the Middle East and Afghanistan.