Why does this bother you when major cities log shooting death counts like this every day? I guess as long as the murders are 'civilized' and one-on-one and not *gasp*

a "mass murder", everything is cool.
Similar to plane crashes vs car crashes.
One difference is the number of people and families affected by the impact at once.
When it is concentrated in one incident, it is perceived, processed and presented in the news differently than multiple incidents over several regions that might kill or injure 1-3 people each.
Car wrecks that kill an entire family of 5 also will draw more attention and weight than 5 different accidents killing 1 person each.
This also affects how the MEDIA responds, if an incident seems "out of the ordinary" (where car accidents or gun violence "that happen on a regular basis" don't get as much attention as an incident that "stands out" because of the numbers killed, or children dying or something else the media can feature that makes this different and stand out)
Another factor is perception of CONTROL and responsibility for the deaths.
People feel more in control of cars they drive themselves to avoid wrecks, vs planes or trains that rely on systems or drivers/pilots we don't control.
And similarly, if mass deaths occur because of ONE shooter, the focus goes to what caused or could have prevented that (either blaming the shooter, the access to guns, the mental or criminal illness, the impact of drugs etc.)
And finally there is some collective conscience, spiritual or karmic factor.
If people sense a connection, or believe there is a reason or a sign of a certain problem the incident represents, they will respond likewise, either consciously or subconsciously. We are all connected socially or spiritually on some collective level. The closer an impact affects you, one person may respond more than another.
This is why people may blame different things or respond in different ways.