The number of workplace homicides is less than half of what it was 20 years ago.  

 Omar Thornton was fired on August 3, 2010. He arrived for a 7 a.m disciplinary meeting at the Connecticut beer distributor where he worked, and after being shown a video his employer had recorded of him stealing a case of beer, was given an ultimatum: resign or be fired. Thornton signed a resignation agreement before reportedly excusing himself to get a drink of water. That was when the horror began.

Thornton used two Ruger pistols he had concealed in his lunchbox to kill nine coworkers during a 45-minute shooting rampage throughout the facility before taking his own life. It was the deadliest workplace shooting in Connecticut history.

Fortunately, tragedies like this are becoming less common. The likelihood of a workplace homicide is now half what it was in the mid-1990s, according to a recent report by the National Council on Compensation Insurance (NCCI). This trend mirrors a declining national homicide rate, but workplace killings have fallen off even more rapidly. There were 950 in 1993 compared to just 462 in 2009, according to the Bureau of Labor Statistics. This represents a 59% drop-off in workplace homicides over 16 years compared to an overall U.S. homicide rate that fell 49%. The number of homicides has also fallen as a percentage of overall workplace deaths. In 1992, 17% were due to homicide compared to just 11% in 2009. (Auto accidents remain the top killer, holding steady at around 40% of all workplace deaths throughout at least the past two decades.)

The massacre in Connecticut was unusual in another way: the homicides were committed by a coworker. "Contrary to popular belief," states the Spring 2000 issue of Compensation and Working Conditions, "the majority of [workplace homicides] are not crimes of passion committed by disgruntled coworkers and spouses, but rather result from robberies."

In a disturbing trend, however, this is less the case today than it was a decade ago. Increasingly, coworkers are killing coworkers. "The highest share of workplace homicides is still due to the category of robbers and other perpetrators, but that share has fallen from 85% to 69% from 1997 to 2009," states the NCCI report. "Over that same time period, the share due to work associates has grown from 9% to 21%."

This represents a key area of concern for all companies. There is little a company can do about the national homicide rate. And while there is more it can do to protect itself from being targeted by thieves (adding surveillance, physical barriers or security guards, for example), robberies can still happen. There are, however, proven steps a company can take to reduce the likelihood of coworker-on-coworker violence.

Conducting better background screening during the hiring process is one. Other companies have found success by adopting zero-tolerance policies towards aggressive behavior of any kind in the workplace. That may be effective when combined with clear disciplinary actions for offenders. But the federal U.S. Office of Personnel Management recommends one method above all others: vigilance.

"No one can predict human behavior, and there is no specific profile of a potentially dangerous individual," states the agency. But, it notes, there are clear indicators based on FBI research of increased risk of violent behavior.

Any direct threats of harm lead the list followed by intimidation, harassment, bullying or other aggressive behavior. Employees who have "numerous conflicts" with coworkers or display extreme changes in behavior also fit the profile of those more prone to commit violence. If any of these issues are observed by, or reported to, management, they should never be ignored.