On the night of March 9, six people were killed outside of Pittsburgh in what was described as an ambush-style killing. One of the victims was a woman who was eight months pregnant. The child didn't survive, and the medical examiner also ruled that death a homicide.
It was what authorities called a "calculated, brutal" operation. As District Attorney Stephen A. Zappala Jr. of Allegheny County described it, according to The New York Times:
One of the gunmen, who was in the alley, fired a handgun to drive the victims in the backyard toward the house’s porch, where a second gunman was able to pick them off with an assault-style rifle. All of the dead were shot in the head.
But it's fairly likely that you didn't hear about it. Beyond Pennsylvania outlets, it barely made the news.
According to a review of the TV monitoring site TVeyes.com, the shooting was mentioned a grand total of four times on the three major networks the day after it happened. Only one of those mentions came after 6 a.m. There have been no mentions at all since then.
The near-complete absence of that story from the airwaves is owed to a few factors. The predominant one is that the presidential campaign is overshadowing virtually all other stories. Simply put, there is less time and real estate for pieces about gun violence.
It may be because the assault took place in a poorer neighborhood, where shootings tend to draw less attention.
But it also seems true that we've grown desensitized to mass shootings. The regularity with which they happen makes it less and less shocking when they do. No one in congressional leadership or the White House even put out a statement on the incident.