(CNN) – In the past week alone there have been three high profile shootings in this country.

A 15-year-old high school student shot a classmate to death in Oregon; two policeman and another person outside a WalMart were killed in Las Vegas by a husband and wife; and a 26-year-old took inspirations from Columbine, and killed a student on a Seattle college campus.

So are mass shootings on the rise? One professor and criminologist says no.



Northeastern University criminology professor James Alan Fox compiled the data of shootings with four or more fatalities from 1976 to 2012, and found that these incidents on a chart look like an EKG: up and down, not a steady rise.

Fox shares his findings with CNN's "The Lead with Jake Tapper.