Not as it's officially defined by the FBI. It requires, in a single incident, 4 people being murdered. You can of course change the numbers by redefining the words of art as the "study" did, but so what?

Did you even read the Mother Jones article? I can't recall exactly what it said, but I myself picked apart some of the "study's" cited incidents, like the infamous one where couple of reporters were killed, one was wounded, and the killer later took his own life. Which obviously doesn't fit the FBI definition. Others were reported to simply not exist, or at least no one could find any verification.

Is there any hoop you won't jump through to justify tens of thousands of deaths?

"We don't care."

Are you from the U.K.? (A guess based on your comment history, word choices, Commonwealth spelling, etc.)