With one more mass killing in America Thursday added to three others over the last three months, people might begin to see a trend forming.

But according to NIU sociologists, there is no way of predicting these instances.

Thursday’s mass shooting in Royal Oak, Mich., which involved a fired postal worker who killed four people and wounded five others before shooting himself, came just one month after a gunman opened fire in a cafeteria in Texas and just weeks after an Iowa State University student went on a shooting rampage.

Associate Sociology Professor James Massey said for there to be a trend, there needs to be “several instances of the event over a protracted period of time.”

“From the perspective of sociologists it’s hard to explain or predict single instances of any type of crime or criminal event,” he said.”

Sociology Professor Joseph Harry said sometimes with mass killings, imitation occurs.

According to an Associated Press article, the gunman joked about the mass shooting at a cafeteria in Killeen, Texas, and said he would do the same.

arry said, “These imitations tend to occur among people that are already unstable.”

Sociologists do not view mass shootings as routine shootings, because a basic factor in mass shootings is that the unstable person came to a breaking point, he said.

But Massey said, “There might be a whole host of factors related to a unique situation.”

Another factor involved with mass shootings is that sociologists tend to think they are planned out, Massey said. “One of the things that makes these kinds of events different from homicide in general would be the evidence of premeditation.”

arry also said these killings are not the everyday shooting incidents that occur on the spur of the moment.

Also, three of the gunmen in the last four mass shootings shot themselves. Harry said the combination of homicide and suicide is common in mass shootings.

Massey agreed, “It seems like it’s relatively rare for the individual in this sort of event to walk away from it.”