The killer, it was learned afterward, had been viewed by some of his acquaintances as a terrific guy.
And that underscores a central reality for employers and the labor and employment lawyers who advise them on how to handle workplace conflicts: Identifying the one-in-a-million person on the verge of committing mass murder is akin to finding a needle in a haystack.
"It scares the heck out of me every time I advise the employer to go ahead and fire the guy," says Michael Ossip, a partner in the labor and employment practice at Morgan, Lewis & Bockius L.L.P. "I always counsel people: Make sure you know exactly what you are doing, because once you let someone go, you lose control over them."
Fred D'Angelo, a labor and employment lawyer at Buchanan Ingersoll & Rooney P.C. and based in Philadelphia, said one tragic error made in the Connecticut case was that the employer permitted the dismissed employee to go unescorted to an adjacent room, where he retrieved two handguns concealed in a lunch box.
Even so, D'Angelo, who happens to represent many of this region's beer distributors, says he doubts employers can change much.
That's because horrific workplace killings, though they rivet national attention, are so unlikely that it wouldn't make sense for employers to dramatically reconfigure their workplaces.
Employers seem to recognize this. D'Angelo, who counsels employers on how to deal with workers who are about to be disciplined or dismissed, says he has never been asked by a client about what to do if an employee shows up with a gun.
The worst case of workplace violence he ever dealt with, and he has been at this for 35 years, involved a shop steward who threw a punch at his supervisor and was dismissed on the spot.
So does that mean society must simply accept a certain level of workplace carnage as the cost of doing business?
Actually, no. D'Angelo says employers need always to be alert for signs that an employee is troubled. Once an employee is about to be dismissed, the employee must remain under supervision until escorted off the grounds and should be observed cleaning out his or her desk.
Ossip says he advises clients, if the employee has made threatening statements, to bring security into the building in advance of a dismissal or disciplinary action. He also suggests taking such action at the end of the workday, when most employees have left for home. Sara Begley, a labor and employment lawyer at Reed Smith L.L.P., also urges employers to have security present.
"Can you take the risk [of not having security] when you are responsible for ensuring the safety of others? The easy answer is you cannot," she said.
But it is a mistake to assume that such measures can always protect against the one employee about to engage in mass murder. After all, many workers, and their managers, can be sullen and withdrawn at times.
Spotting a weapon in a company parking lot might not tell you much. There are many parts of the country, including Pennsylvania, where it is common for workers to stash a rifle in a pickup truck for deer hunting.
Following the Columbine killings in April 1999, hundreds of psychologists, educators, and law enforcement officials convened in Leesburg, Va., to brainstorm about things that parents and community leaders could do to protect children from attacks in schools.
There was plenty of research to draw on, including a landmark study by University of Wisconsin psychology professor Leonard Berkowitz, who found that violent crime spiked for several months after the assassination of President Kennedy, and after the mass killings committed by Charles Whitman and Richard Speck. The study seemed to confirm the impact of media coverage on the so-called copycat effect.
After Columbine, the lives of the killers, Dylan Klebold and Eric Harris, as well as other school attackers, were carefully deconstructed.
The disturbing truth was that, while the shooters had dropped hints, they weren't terribly obvious about it.
They weren't loners. They even had good-to-adequate grades. Their true natures were not revealed until they had killed their classmates. Clearly, they had not been identified as dangerous. Yet, not reviewing for missed signs would have been unthinkable.
As one school-safety analyst with the National Education Association said after the Columbine shootings, "It's very, very difficult to know when these incidents are going to happen - but you have to try."
Contact staff writer Chris Mondics at 215-854-5957 or firstname.lastname@example.org.