"It was so loud ... you could see the cleaners running down the hall and getting thrown against the wall."
The group waited for the initial shaking of the 8.1 magnitude quake to subside, then "gave it 30 seconds before grabbing our passports and running out".
They spent the next two days living in a nearby garden as the ground continued to shudder beneath them. Rumours of massive aftershocks spread more terror through Kathmandu's rubble-strewn streets.
Then, after hours of waiting and delays at a chaotic Kathmandu Airport, the group eventually made it on to flights out of Nepal.
But the decision to leave had not been easy.
"It almost felt like cheating," Dr Reynolds, 26, said. "[But] we had no disaster skills and we would have just been taking up food and water.
"It was a feeling of helplessness that we couldn't do anything."
That feeling of helplessness has inspired the couple to do what they can from Rotorua to help the relief effort.
On June 10, they will host Feature Nepal, a night of films at Waiariki Institute of Technology. Coincided to time with the Banff Mountain Film Festival, the event will show clips of adventure sports like mountain biking and paragliding, all set in Nepal.
"It's a chance to see some really epic films, and get a slice of Nepali life," Dr Reynolds said.
Nepali snacks will be on offer at the event. Ms Gray said that, as well as raising money, she hoped the film evening would be able to "sell" Nepal to those who may now just associate the country with danger and tragedy.
"They need the tourists to go back, it's their only income," she said.
The event will cost $20, and all money raised will go to two organisations involved in the relief effort.
One of those is Tamkoshi Co-operative, the umbrella organisation of the hospital where Ms Gray worked.
The other is Nepal Cyclists Ride to Rescue - a charity run by the country's national mountain bike team, delivering aid to isolated rural areas.
The couple remain deeply affected by their time in Nepal - but it is the suffering of the Nepali people that they can never forget.
"It hasn't left my mind. Not really my own experience, more the experience of the people I worked with," Ms Gray said.
Dr Reynolds said: "The people are so gentle and so friendly, and manage to do so much with so little."
It is not hard to imagine the couple returning to Nepal one day to help with the rebuilding effort.
But if they do ever make it to Langtang National Park, they won't be able to visit the local village, once home to 200 people.
"It doesn't exist any more."
-See "Feature Nepal: a Night of Adventure Films in support of Nepal" on Facebook.
