It's maybe the most annoying response on the internet, communicating that You, Observing A Bad Thing, are stupid for Being Surprised By Something Not Surprising.
Me: Wow, a mass shooting. Bad.
You, Wise Person: And you're surprised by this? Don't you know about all the guns???
No most of the time this stuff is not surprising. It's also the twin of "that's just the way the system works." Well maybe it shouldn't?