PORTLAND, Maine (NEWS CENTER) -- A couple from Las Vegas happened to be visiting Maine when they turned on the TV, and saw the terrible news. Their hometown had been attacked by a lone gunman.

"For some reason the first thing I said to Allison when I saw him on the news was, 'I know that guy.' I recognize his face and I'm really good with faces," said Brian Campbell.

Brian and his wife Allison own Campbell Defense Academy in Las Vegas. Brian said he had a booth promoting their business at the Crossroads of the West Gun Show last month. That's where he claimed to have interacted with the Las Vegas gunman, Stephen Paddock.

"We have firearms on the booth to gather people's attention. And he came up and started questioning me about all the things with the rifle," said Brian. "It's not uncommon to see people at the gun show quite often."

Police have not released what kind of weapons Paddock used in the attack that murdered 59 people, nor released if Paddock recently attended any gun shows. Two store owners in Nevada told investigators Paddock bought firearms from them-- but both said those weapons were not automatics.

On Tuesday, officials said Paddock may have modified his weapons to fire faster. We asked Brian and Allison if that was easily done:

"It is," said Brian.

"As a matter of fact you can do it in a matter of minutes," said Allison.

Allison sent us a video she put together for YouTube. It shows a semi-automatic weapon with a binary trigger attached.

"it's completely legal, because it's not automatic, not pulling in one shot. It's pull and release. But by doing it quickly you can probably shoot 30 rounds in 2.7 seconds," explained Brian.

Allison's video shows exactly how fast it fires. A semi-automatic with the binary trigger fired 30 rounds in 2.7 seconds. An automatic weapon fired 30 rounds in 2.9 seconds.

Investigators in the Las Vegas case say they are aware that a bump stock may have been used by the gunman.

"You know when people dribble a basketball and it goes really fast? Same situation when that bump fire hits your shoulder," Brian explained as he mimed holding the rifle. "When it rebounds off your shoulder, it causes your finger to keep pulling the trigger.That can probably shoot 30 rounds in three seconds."

Allison said the Mainers they met on their travels have been incredibly supportive.

"They've sent donations and food. They're showing a lot of love and a lot of support out here."

"I'm glad we are here to see it-- the love and support from the people of Maine," added Brian.

The couple was on their way back home Tuesday afternoon. Allison said she plans to hold a candlelight vigil at the famous Las Vegas sign on Thursday.