US journalist killer `annoyed` colleagues: Ex-boss

The disgruntled former US television station employee who murdered two journalists had "annoyed" colleagues but showed no signs at work of any mental health issues, his former boss said Thursday.

Vester Lee Flanagan, 41, worked as a reporter for WDBJ in Roanoke, Virginia from March 2012 to February 2013, but was dismissed for poor performance and angry behavior, general manager Jeffrey Marks said.

On Wednesday, Flanagan shot and killed two of the CBS affiliate`s journalists while they were conducting an on-air interview. He later fatally shot himself.

"We are still at a loss to figure out what happened to him in those two and a half years" since he was fired, Marks told a news conference flanked by dozens of staff, many of them holding hands.

"I don`t think we identified that he had mental health issues. We certainly identified that he had performance issues."

Marks defended the station`s hiring record and said its parent company had "a very elaborate program to screen employees."

Flanagan passed background checks and came with only positive references, Marks said. 

It was only after he was hired, Marks said, that things went downhill.

"Vester`s behavior annoyed a lot of people in the news station," Marks said.

Flanagan, who went by the on-screen name Bryce Williams, alleged in a manifesto faxed to ABC News that he was discriminated against as a gay, black journalist.

Marks said accusations in 2013 that he was treated unfairly were "immediately investigated and found to be without merit."

During his employment, Flanagan complied with demands that he seek medical help, but he was ultimately dismissed.

He was escorted from the building by police and made an ominous aside to the news director -- handing him a wooden cross and saying "`you`ll need this`," Marks said.

As he left, he also made a "derogatory comment" to Adam Ward, the cameraman he shot dead on Wednesday.

Flanagan filed a complaint with the Equal Employment Opportunity Commission and a civil action suit, which were dismissed, he said.

"All of these investigations determined that no reasonable person would have taken any of the cited incidents as discrimination or harassment."

After killing Ward and reporter Alison Parker live on the air, Flanagan posted a video of the attack on social media.