Virginia Shooter's Ex-Boss Tells of His 'Abrasive' Behavior

Vester Lee Flanagan threatened to hit one of his colleagues when they were on a reporting job years before he fatally shot a reporter and a cameraman this week, his former boss told ABC News.

Dan Dennison, the news director at WDBJ when Flanagan worked there, said that everything was going well with his employment for the first two months after he was hired in March 2012. It wasn't until May of that year that he had his first run-in with a colleague that happened when Flanagan, who went by the name Bryce Williams at work, was called to report a story in the field with another reporter.

"He allegedly entered the station microwave truck, or live truck, and started screaming and yelling at a reporter and a photographer, or maybe two photographers in the truck," Dennison told ABC News in his first interview since the shooting on Wednesday.

Dennison learned about the incident after the other staffer, who was not named, told Dennison about the incident but they decided not to file a formal report at the time because they "tried to work things out," Dennison said.

"We really thought it was a one-time situation at that time," Dennison said.

Greg Baldwin, who works as the assistant news director at WDBJ and worked at the station at the same time as Flanagan, reiterated that account and said that it served as a warning sign.

"The reporter calls me and she says, 'You have got to get here now. Bryce has -- we got into an argument and he is in my face. And I, I think he is ready to hit me,'" Baldwin told ABC News.

"That was the first time that we knew that he was violent," he said.

Dennison said that the "pattern" of complaints relating to his "brusque and abrasive demeanor" came mostly from his colleagues but also from one or two people in the community who he interviewed as part of his job.

Dennison detailed the various meetings they had with Flanagan before he was fired on Feb. 1, 2013, which were echoed in a court filing publicly available as a result of a suit Flanagan later filed against WDBJ. The suit was later dismissed.

The tipping point came when the human resources director presented Flanagan with his severance package.

"He took one look at that and cussed and said, 'This is B.S.,'" Dennison said.

"As I recall, he slammed his fist down on the table," Dennison said. "It was so loud, people frankly reported that they thought a bomb had gone off."

The situation escalated from there, so much so that they had to call in two police officers to help escort him from the building. Dennison said the officers spent five to ten minutes trying to get him to leave his desk.

"At one point, I was standing maybe five feet away from him up against the wall, and he looked at me and threw a ball cap and a wooden cross at me and said, 'You're gonna need these,'" Dennison said.

He wasn't the only one to spark a reaction from Flanagan, Dennison said.

"Adam Ward -- the young man who was killed -- was standing in a back corner of the newsroom, videotaping this for documentation. And Bryce turned around to him at one point and flipped him off and cussed at him," Dennison said.