(CNN) The job offer seemed a promising start for Vester Flanagan : He would be a multimedia journalist using the name Bryce Williams at WDBJ making $17.31 an hour, or $36,000 yearly, in early 2012.

But it took only two months on the job for him to receive a written note in his personnel file about how he made co-workers feel "threatened and uncomfortable" with abusive verbal and body language on three occasions, according to court documents.

Two more months later, Flanagan faced a written warning that he would be fired unless he improved immediately. His harsh language and aggressive gestures were causing "a great deal of friction" with photographers and other co-workers at the TV station in Roanoke, Virginia, documents say.

Supervisors ordered him to get help through an employee assistance program because of his "anger and his inability to work with colleagues from time to time," said Jeffrey Marks

Flanagan complied. But in the end, he was fired after 11 months on the job.

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On the day he was fired -- February 1, 2013 -- the station's human resources representative called 911 because Flanagan warned, "I'm not leaving, you're going to have to call the f***ing police. ... I'm going to make a stink and it's going to be in the headlines."

Flanagan tossed his news director a small wooden cross and added, "You need this."

The director then cleared the newsroom, and police removed Flanagan.

Flanagan's brief, troubled tenure at WDBJ was revealed in court papers filed in his lawsuit claiming racial discrimination and wrongful termination. A Roanoke city judge dismissed the lawsuit on July 2, more than a month before Flanagan, 41, went on a rampage and killed two station journalists and then himself.

Trying to understand why

A day after the shootings, WDBJ executives struggled to say what they could have done differently with the troubled employee.

"There were probably things we can do," Marks said. "We can probably screen more, but by and large we get great employees here. One is going to slip through the cracks every now and then. I'm very proud of our hiring record."

Station employees said they had interacted with Flanagan without incident since he was fired, which makes his actions this week all the more baffling to them, Marks said. Flanagan lost his complaint filed with the Equal Employment Opportunity Commission, he said.

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"We're still at a loss to figure out what happened to him in those 2½ years," Marks said.

Before hiring him, the station called Flanagan's references, who all gave positive reviews, he said.

But Marks noted: "It's very hard to get a negative reference these days. Most companies have policies that forbid their people from giving references. And so what you get a lot of is name, rank and serial number.

"I think anybody can make positive references happen if they try hard enough, so we exhausted what we could on that," he said.

As for Flanagan's on-air and writing ability, Marks said that "I don't think he was the strongest quality applicant we've ever had, but he passed muster of the news management team at that time."

A dangerous 'injustice collector'

Flanagan displayed traits of what a former FBI profiler calls "an injustice collector," someone who blames others for their problems, asserts nothing is their fault and contends everyone is insulting them even when it's not true.

But Flanagan seems to have been a dangerous kind of injustice collector, because he showed aggression and made threats, said Mary Ellen O'Toole, a psychologist and a former FBI agent for 28 years who worked in the Behavioral Analysis Unit.

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More professionals are offering expertise and guidance to corporations, businesses and universities on how to fire or expel potentially violent people such as Flanagan, she said.

"We get calls all the time on how do you fire this person," O'Toole said.

A psychologist, police officer, security expert, or mental health professional is hired to keep in touch with the individual even after he or she has been fired, she said. This new field is advanced by the Association of Threat Assessment Professionals, O'Toole said.

"Just cutting ties with him may feel good, but you have no idea of what you unleash," she said.

The post-firing service is designed to defuse any potential violence and help the individual get on with his life, O'Toole said.

"It's a new normal," she said. "It allows you to sit down with someone, and you do it in a very therapeutic and supportive way."

Monitoring includes whether any police reports have been filed against the fired employee for violent behavior.

"I know people will say that will cost a lot of money. I'm talking one person out of 100 or maybe 500 who gets fired" who may be potentially dangerous and need the service, she added.

"It's not a perfect science, and it never will be, but we're pretty good at it," O'Toole said.

Newsroom films Flanagan's outburst

Flanagan's dismissal and confrontation with police were so dramatic that staff photographer Adam Ward picked up a camera and recorded the moment in the newsroom. On the day police led him out of the office, Flanagan snarled at Ward, saying "lose your big gut." Flanagan then flipped off Ward's camera.

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They were interviewing Vicki Gardner , the executive director of the Smith Mountain Lake Regional Chamber of Commerce, near Moneta, Virginia. Gardner, who was wounded, was in stable condition after surgery. Her husband said a bullet grazed her spine.

Authorities are still investigating the circumstances of the shooting, but Flanagan left behind a 23-page note that lists his grievances.

Trouble with performance, too

The station's internal records about Flanagan, filed in a Roanoke court, also show that he was performing poorly on the job in some areas.

His August 2012 performance review gave him an "unacceptable," the lowest score on a scale of 1 to 5, on his ability to work with photographers, producers and assignment editors.

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"The area where Bryce must make immediate improvement is with photographers," wrote his supervisor, David Seidel.

Flanagan also wasn't contributing to the Web frequently enough, receiving a scoring category that is listed as "has an opportunity for improvement." That amounted to a score of 2 on the 1-to-5 scale, with 5 being the highest score.

"Bryce needs to incorporate web posting into his daily schedule," Seidel wrote.

Flanagan confronts anchor over his script

By December 24, 2012, station news director Dan Dennison told Flanagan that despite a lot of coaching, "you seem to have reached a plateau," according to an internal memo.

Dennison cited recent examples of Flanagan's "lack of thorough reporting, poor on-air performance, or time management issues," documents said.

Dennison said Flanagan reported straight from a news release "instead of doing some original reporting," documents said.

Flanagan also filed "gratuitous coverage and promotion" of a church instead of using "critical thinking and questioning skills to produce truly memorable television stories," Dennison's memo said.

And Flanagan continued to have problems with cameramen; he was "curt and defensive" with one photographer who questioned him about staging an interview, Dennison's note said.

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Even with the written warnings, Flanagan didn't show improvement.

In January 2013, the month before he was fired, Flanagan was the subject of several internal memos about his performance and conduct.

Two days before he was fired, producer Kim Pinckney sent a note to Dennison about how Flanagan "created an uncomfortable situation" for anchor Nadia Singh because Flanagan questioned her authority to review his script.

Dennison then wrote human resources representative Monica Taylor about how the anchor described Flanagan as "very confrontational" and "defensive."

"Nadia says she couldn't figure out initially what he was driving at and (he) kept making the point that he had as much experience as she does and why is she 'approving scripts,' " Dennison wrote Taylor.

Dennison and Taylor fired Flanagan two days later.