It happened years ago, but the scene is still fresh in Carol's mind: Her onetime boss pinning one of his young employees against a wall in a conference room and landing multiple punches on her face.
From her nearby desk, Carol, who asked that her real name not be used, saw it all.
"He just went into the most violent rage that I'd ever seen in my life," she said. "There was blood everywhere."
At the time, Carol worked at a medical school that is part of Yale University, which recently saw the murder of one of its graduate students, Annie Le, allegedly at the hands of a co-worker at a university lab.
The murder has raised new questions about workplace violence across the country and brought back painful memories to people like Carol, who quit Yale Medical School shortly after the incident she witnessed in the summer of 1999. (A current employee at the medical school, who also asked not to be named, and Yale's clerical workers' union confirmed the incident. Yale University and New Haven police did not immediately return calls from ABCNews.com. UPDATE Wednesday, Sept. 23: In a report provided to ABCNews.com by New Haven Police, the man accused of the beating said that the injured employee lunged at him after a disagreement and that he was defending himself. A police detective investigating the case concluded that the man was telling the truth.)
Despite the headlines, statistics show that workplace violence is still uncommon.
"If you look at workplace homicides in any one year, they're typically at 1,000 or under, across the whole U.S., among 150 million workers," said Tom Tripp, a Washington State University management professor and co-author, with Georgetown University management professor Robert Bies, of "Getting Even: The Truth About Workplace Revenge."
"That's a thousand too many," Tripp said, "but statistically speaking, it's really rare."
Incidents of workplace violence other than murder are quite high. In a 2005 survey of 7.1 million private businesses, the Bureau of Labor Statistics found that 5 percent -- more than 350,000 businesses -- reported workplace violence in the 12 months before the survey.
But Tripp noted that the definition of workplace violence used by various studies is more expansive than some might think: It can include verbal threats and bullying, as well as physical acts. Oftentimes, the perpetrators of workplace violence are not the workers themselves but rather third-parties, such as robbers, customers or aggrieved spouses.
"A very small percentage of it is by co-workers," he said.
Preventing Workplace Violence
Washington State's management professor Tripp said employees can take steps to prevent violence among co-workers by making sure they report all threats to their superiors or police. Employers, meanwhile, he said, should establish systems to address employee complaints.
Carol, the former Yale employee, said that in retrospect, there were signs that the supervisor could be dangerous.
He was "moody" and hostile, she said, and frequently called people by offensive, obscene names.
Raymond Clark, who was arrested in the Le case, was described by some as a "control freak" who was upset at how Le handled mice at the lab where they worked.
But Tripp said that many people who exhibit hostile behavior in the workplace never do turn violent, while some who commit violent acts show no warning signs.
Whether it's expected or not, what can make the aftermath of a violent incident worse is when it appears the perpetrator hasn't been penalized for his or her actions.
Carol said that the supervisor kept his job for months, and that, as far as she knew, the only penalty he ever received was eventually being moved to a different department.
Laura Smith, the president of Local 34, the Union of Clerical and Technical Employees at Yale, said there were repercussions following the incident but couldn't specify what they were.
"I think we ended up in a place that we felt was reasonable," she said.
After an incident of workplace violence, Tripp said, it's important for employers to be transparent in how they penalize the perpetrators involved.
If companies allow employees to believe that no penalty was handed down, it could, in some cases, encourage more workplace violence, he said.
"I can imagine anyone thinking, 'What are the consequences if I get violent? They didn't do anything to these other people, they wouldn't do anything to me,'" he said.
"You have got to have some equivalent of law and order in the organization," Tripp said.
ABCNews.com asked readers to share their experience with workplace violence, whether it was verbal or physical. While Carol's was one of the most egregious stories we heard, other readers had their own disturbing tales, including the ones on the next page.
Locked in a Vault
Cynthia, a California resident, once worked at a job that included financial auditing and the supervision of workers. After several audits, she began to suspect a vending technician at her company of stealing and asked that he move his desk into an area where he could be more closely observed by others.
In a message to ABCNews.com, she told this story:
"The day I arranged to do this he showed up for work disheveled and somewhat in a haze. He tried to get me to stop the move, but I let him know it was going to happen. He proceeded to coerce me into the walk in [a] vault under false pretense. Then he quickly locked me in and turned off the lights trapping me inside. When I was freed from the vault , the employee was put on immediate suspension awaiting removal from the organization."
The man was ultimately reinstated, however, and Cynthia said he continued to frighten her by muttering threats under his breath. Frightened, Cynthia said she began to have breakdowns in the office and was eventually told to go on medical leave.
"I was fortunate that he did not kill me," she said, "but I will never be the same."
The Pointed Gun
Stacy, an Alabama resident, found her pizza parlor co-worker "creepy."
"This guy would try to corner me and hug me, and he would follow me around the store," she wrote in a message to ABCNews.com.
But things grew much worse when the man purchased a handgun, she said.
He tried to coerce her out of the restaurant, she said, and into his car so he could show her the gun, but Stacy said she declined.
"He hated the fact that no one was interested in his gun," Stacy said. "Finally, he ended up pointing the gun at my friend in the parking lot as a 'joke.'"
But neither Stacy nor her friend found it funny at all. Both quit the pizza parlor, though the creepy co-worker kept his job.
Listening for Gunshots
A Texas man remains so fearful of a co-worker he knew 10 years ago that he asked that ABCNews.com withhold his full name. This is his story:
"I had a co-worker who had a history of mental problems, was taking medication and could not sleep at night. He told stories of pulling guns on people. He had been in law enforcement when he was young.
"He had a crush on a single woman at work and was buying her expensive gifts. When she told him she wanted nothing to do with him he wrote a very scary note and left a copy in each employee's inbox. It was a bizarre note about how bad he felt about his hatred for his fellow co-workers.
"So the woman was relocated and the nutcase returned to work in a couple of weeks, commenting how management and HR were afraid of him. He even carried a rifle/shotgun case to work one day after the incident and laughed that everyone was too afraid to confront him about the case.
"Since the nutcase could not sleep he would come to work as early as 5 a.m.. I came to work early at 7 before most of the employee,s and I honestly listened for the sound of a handgun, rifle or shotgun mechanism every morning when I entered the building and contemplated what action I would take to escape.
"This guy scared me to death. I transferred out 10 years ago, and the employee since retired, but I will never forget how scared I was with him at work."