So what can companies do to help prevent a similar tragedy? Experts say companies and their colleagues can take many steps, which may seem surprising:
After the shooting in Aurora, some wondered if companies should have an armed guard in the room when an employee is fired.
But that's usually not a good idea, said Steve Albrecht, co-author of "Ticking Bombs: Defusing Violence in the Workplace."
It is not known if the Pratt Co. had security in the room. But Albrecht said that the sight of a uniformed guard "raises the emotional temperature of the employee being fired," causing thoughts such as "Why do you have this guy with a gun in the room with me? Do you see yourself as a threat? "
These feelings of resentment and anger may last long after the end of the shooting meeting.
Albrecht, an expert in threat assessment, said it was best to have an armed guard nearby, but not inside – perhaps by listening to the meeting by telecom or in front of the door. It is also wise to have a code word so that the guard knows when to intervene and intervene.
Another solution is to put on a plainclothes armed guard at the closing meeting.
"I often use plainclothes security guards who will be in the room and we introduce them as a human resources consultant," Albrecht said. "They can be practical if necessary."
Do not assume that you are immune
"The point of layoff is perhaps the greatest opportunity for deadly violence in the workplace," said Kathleen Bonczyk, Founder and Executive Director of the Workplace Violence Prevention Institute, non-profit.
Bonczyk said that long-term employee layoff may present the greatest risk.
"It's almost like a divorce from a family," she said. "Today, Americans tend to spend more time at work than at home, they tend to have more lunches, dinners, meals, time with colleagues. perhaps the most stable relationship an employee can have. "
Albrecht said that companies should not assume that an employee would never commit violence just because he had no criminal record.
"There are people who have a criminal background that does not pose a threat to their employers, and those who do not have a criminal record" who could break, he said.
This highlights the need to:
Help the employees well before they're fired
It is normal for employees to become very emotional when they are fired. But the trauma can seem overwhelming if someone struggles with other personal issues, such as divorce.
It's also a good idea to extend EAP coverage for a while after an employee's dismissal, said Albrecht.
Do not give notice, except in case of layoff.
The Aurora shooter had already been drafted and probably knew that he was going to be fired, said the CEO of Mueller Water Products, parent company of Henry Pratt Co.
"We can assume that he was speculative about what was going to happen, as evidenced by the fact that he was armed with a gun," said managing director, Scott Hall. "I do not know exactly what was communicated to him."
Although it's not clear if the shooter was warned in advance, Mr. Albrecht stated "that it's best not to give notice to any particular employees" s & # They are fired.
However, with regards to the layoffs, Albrecht stated that companies should inform the office before employees are dismissed.
"In my experience, collective redundancies are causing problems," he said.
Instead, companies should offer job search services or allow employees to work on their resumes during work hours – "human things," Albrecht said.
"There is just less animosity, less desire for revenge when treating people like adults."
Do not let dismissed employees with anything
It is important that an employee's anger is not made worse by the desperation.
"A lot of organizations have what's called a benevolent separation, which gives them a cushion, a soft landing," said Albrecht.
This may include severance pay or a temporary extension of benefits, such as employee assistance programs.
Such offers let employees know that the company does not think they are "a horrible person," said Albrecht. Instead, it shows that they "just do not fit in. But here's what we do to help you get back on your feet."
Stay alert after the dismissal of employees
All cases of violence in case of dismissal do not occur when someone is fired, as in Aurora.
"Sometimes it takes less than two weeks or two years," said Albrecht.
He added that the violence could occur up to two weeks later, when employees are still "super angry" and have time to create a plan.
But sometimes, the violence does not occur until two years if the employee is unhappy did not find work at that time.
The best strategy for preventing future violence is "listening to leaks" because those who plot attacks often confide in someone else, said Albrecht.
Thus, employers must keep in touch with the person's friends who are still in the business and make sure they feel comfortable reporting any disturbing comments or any threats .
Although filming Aurora may seem unpredictable, it's time for everyone to take precautions, Bonczyk said.
"I hope people will take this opportunity to learn from this tragedy and look at the gaps in their workplaces," she said.
"The time to think that it can not happen here, that it could not happen too, is over."
Ray Sanchez of CNN contributed to this report.