ROANOKE, United States (AFP) - Kimberly McBroom, who was anchoring the morning news show on WDBJ when two of her colleagues were gunned down on-air, says that even after she heard "popping sounds," murder did not occur to her.

Only when she and her colleagues heard a voice through the live audio feed say "three down" did the gruesome reality settle in that reporter Alison Parker and cameraman Adam Ward were in trouble.

"I thought, 'Anything but'," McBroom told reporters outside the television station Thursday after ending her programme, which included a moment of silence in memory of the slain pair.

"They were at the lake. They were doing a feature story. It wasn't a standoff; it wasn't any dangerous situation - just a feature."

It was towards the end of WDBJ's Mornin' show on Wednesday when Parker and Ward were doing a live interview about tourism development from a lakeside town outside Roanoke.

It was the kind of story that is routine stuff for local television stations throughout the United States on any given day.

Parker, 24, and Ward, 27, were also typical of the young, bright and ambitious American journalists who start their careers in small-town news.

Then along came Vester Lee Flanagan, 41, a reporter at WDBJ until he was fired in 2013 and a self-described "human powder keg" filled with anger.

With a handgun, he killed Parker and Ward, wounded their interviewee, a local chamber of commerce official, then fled by car, only to fatally shoot himself when police caught up with him.

In the studio, McBroom - a mother of two who like many WDBJ personnel is a native of the Roanoke area - was seized with disbelief.

'DID SOMETHING BLOW?'

Hearing "popping sounds" and seeing Ward's shoulder-mounted video camera falling to the floor, McBroom thought: "That's weird."

"Did Adam's light go out on his camera? Did something blow? It's a rural area so (someone) could have been firing shots in the distance," she recalled.

"There were, like, 10 different things that went through my head. This (murder) was not one of them at all."

But the live audio feed kept rolling, and McBroom and her studio colleagues - including Ward's fiancee Melissa Ott, the morning show producer, on her last day on the job - started worrying.

"We were trying to text them. 'Hey, what's going on? What was that?' We didn't hear anything. No response," she said.

"The longer we went on without hearing a response from them, the more it was very clear to us that something was very wrong."

Only after the hourly newscast did a voice, possibly from a responding police officer, come over the live audio feed.

"We heard 'three down' and then our morning editor, who was watching the feeds, came over, upset, and told me," McBroom said.

'HOLDING ON TO HOPE'

Suddenly finding themselves becoming the story, and shock beginning to stir their emotions, the WDBJ news crew in the studio stuck to journalistic principles.

"Of course we were waiting to hear confirmation - how many people were shot, how badly were they hurt," McBroom said.

"We kind of had to handle it like journalists, but we can't jump to conclusions. I think in our hearts we knew it was bad," she said.

"But until you get that confirmation, you don't know, and you're holding on to hope. Man, we were clinging to it." McBroom admitted that coming to work on Thursday was not easy.

"I was dreading it because I knew it was going to be just horribly difficult," the WDBJ anchor said.

"But I knew I had to come... I'm just trying to do my job and honor their memory and do what they would have done." On her purple dress, McBroom wore a memorial lapel ribbon created by a WDBJ employee.

It featured two colours - turquoise, thought to be Parker's favorite shade, and maroon, for Ward's alma mater, nearby Virginia Tech University.