Monday's shooting at a Baltimore, Maryland high school and last week's shooting at the Empire State Building, as with the buzz surrounding them, seem to have become all too familiar.
With similar incidents at the Family Research Center in Washington, D.C., the campus of Texas A&M University, a Sikh temple in Milwaukee, and a movie theater in Aurora, Colorado, the headlines in the United States have been particularly violent this summer.
"This appears to be what will be one of the worst years ever in terms of homicides at work, worship, and obviously in terms of school shootings," says Dr. Larry Burton, an expert on workplace violence and professor at Bryn Mawr College. "Something is going on that is generating such a spike in these cases."
What that "something" is exactly is hard to say, but the more coverage such violent events get, the more likely some will imitate the perpetrators, Burton says.
"It appears that part of it is copycat situations," he says. "These situations unfortunately do prompt other people to say 'I can do this.'"
The headlines don't necessarily mean this year has been particularly bloody.
"The frequency of gun violence does not fluctuate much year to year, it only seems that way because we look for the trend," says James Alan Fox, a professor at Northeastern University.
"Earlier this year, in Seattle, five people were shot and killed, not many people have heard of it," Fox says. "But if that happened next week or next month, it would be all over the news."
"We haven't had much more (mass killings). They occur anyway and now you're on the lookout," says Fox.
Fox says there is no constant tally on such shootings in the U.S., in part because the criteria is hard to pin down. Last week's shootings in Chicago, in which 19 people were shot across the city over the course of a few hours, doesn't have much in common with what happened in Colorado. We might lump serial killers in with incidents like Aurora, but those are also different—the FBI would not consider a serial killer's actions "mass killings" because they occur at different locations.
But it is safe to say that with each passing year, the number of mass killings and violence related to guns in the United States has increased when compared to countries of similar political and economic makeup, Fox says. According to the United Nations, the U.S. has higher firearms ownership rates, and more civilian-owned firearms overall, than most of the world.
Though the U.S. does have a greater overall crime rate, there are a number of reasons to explain the disproportionate amount of gun violence. One common explanation is the nation's laws and governmental policies are to blame.
"We do have a breakdown in our mental health system," Burton says. "Tens of thousands of patients in past few years released due to budget cuts. Then there's the availability of weapons and ammunition, you could argue that plays a part."
Despite the calls for stricter gun controls and better mental health guidelines that seem to arise following each incident, policy rarely changes.
Instead, the strategy appears to be aimed at stopping individual events before they happen.That can be difficult given the unpredictability of the alleged shooters, though there are some tells, Burton says.
For one thing, shooters are typically what Burton calls "grievance collectors," people who harbor intense feelings of disrespect for perceived slights, such as being passed over for promotions or being relocated within their career. The more specific the targets of the slights become – say going from 'I'm mad at the world' to blaming a single person in the workplace – the higher possibility of violence.
Another predictive pattern is a significant shift in someone's behavior, Burton says. James Holmes, the alleged Aurora shooter, dropped out of school and died his hair orange. Maj. Nidal Hassan, who is awaiting trial in the shooting at Fort Hood, gave away all his possessions before the attack. Often times these steps indicate someone may soon take drastic action.