Some unexpected sense from CNN in the aftermath of a tragic shooting in Oakland:

 Oakland is reeling after a gun rampage at a small religious college left seven people dead. Six months ago, eight people died in a shooting in Seal Beach, California. And just over a year ago, an attack targeting Rep. Gabrielle Giffords in Arizona left six dead and 13 injured.

Each mass killing provokes a flurry of public shock and a frenzy of media attention — and often soul-searching about whether they represent a broader descent into gun-fueled violence.

But are such attacks on the rise in the United States?

Not according to professor James Alan Fox, a criminologist at Northeastern University in Boston who has been studying mass murder for the past three decades.

Despite the huge media coverage devoted to them, crime statistics show that there is no upward trend in mass killings — defined as having four victims or more, not counting terrorism — since the 1970s, he said.

Campus shootings, such as the Virginia Tech massacre in 2007, or the cluster of school shootings of the 1990s, including Columbine, often attract more attention than multiple killings in other settings. . .  .

“Overall in this country, there is an average of 10 to 20 murders across campuses in any given year,” he said. “Compare that to over 1,000 suicides and about 1,500 deaths from binge drinking and drug overdoses.”

So while they are sad when they occur, school shootings are “very few and far between, and very unpredictable,” Fox said. This suggests that authorities can do greater good by focusing on the prevention of suicide and substance abuse than trying to guard against a campus killer.