Boulder, Colorado (CNN) -- Even though rising floodwaters were wreaking havoc along Colorado's Front Range communities on September 12, Mark Changaris and his roommate, Stephen Smith, felt safe in their upscale home high on a hillside adjacent to Flagstaff Mountain. A mile downhill, downtown Boulder's streets were underwater.
"We thought there might be some minor flooding in the house," said Mark. "We're so high up, we thought there would be nothing to worry about up here."
The drama was just beginning.
In the early morning, Smith heard reports that heavy rain was isolating the city of Lyons, where his sister Catherine lives. He decided to evacuate Catherine; her partner, Mandy; their 8-month old daughter, Tobin; and two family dogs.
Using Google Earth maps and a familiarity that came from riding mountain bikes in the area, Stephen told Catherine, who was reachable only via e-mail, that if she could hike over a ridge behind her home, they could meet at a rock quarry.
"I zigzagged farm roads and dirt roads and found my way to the quarry, where I waited for them, quite anxiously of course." Smith said.
They eventually found one another, and the four, along with the dogs, crossed overflowing drainage channels and steep terrain to reach Stephen Smith's truck.
A soggy, cold but happy Smith drove his extended family back to Boulder.
But not all was well. After the rescue, Smith and Changaris worried that their own home was in danger.
Changaris had to strip down and dive into neck-deep water to unblock a drain filled with mud and debris. Stephen went outside to assess rising water. "The drainage is getting higher," he said.
Within minutes, their backyard filled with floodwater.
"There was a 4-foot wall of water with branches and debris in it," said Smith.
He ran inside and warned Catherine, Mandy, Changaris and his girlfriend, Kristen Huber, to get out.
"The latch on the door was creaking," Smith said. "Everything was about to give, and I knew we were going to get just hurt badly if we stayed any longer."
"It happened so quickly and suddenly," Changaris said. "It went from a very calm, warm and welcoming living room to a disaster in an instant. There was roaring and screaming and the sound of an immense amount of moving water and debris."
Both roommates tried to hold back the French doors.
"The force was overwhelming, and in the back of your head, you're thinking of another slide could be coming down -- something that could be larger," said Changaris.
"We just decided in that instant, just to get out," he said.
After the initial rush of water, Stephen and Mark went back to collect a few treasured items.
Huber used her phone to shoot video of the flood.
"I felt a little guilty," said Smith. "One minute I'm on the highest of highs, feeling like I helped take care of my family -- the people closest to me -- and brought them to what seemed like a safe, warm place where at least we could be together. And then, moments later, I'm walking around the hillside in the rain, with a towel on a baby, barefoot."
Two other roommates were out of town during the landslide. They all returned to thick mud and ruined furniture.
Last Saturday evening, after a grueling day salvaging belongings, an exhausted Changaris sat down to the home's Baldwin grand piano to play "Mad World," the '80s song by the British band Tears For Fears. Roommate Maren Keeley took out her phone and recorded Changaris' poignant rendition.
"It was a beautiful moment in the midst of destruction," Keeley said.
The video has gone viral.
"It's whimsical, it's beautiful, it's sad, and it touches you in a lot of ways," said Changaris. "I think it explains this whole event. This is nature, and nature is beautiful in a lot of ways. It's also incredibly destructive. It's sad, and people are suffering right now."
He has been playing on and off for about 10 to 15 years and says he's never been classically trained.
Changaris, an attorney, is modest in the limelight. He wants everyone to know that people are suffering in Colorado, his home state, and he wants them to volunteer their time or give money to a charity like the Red Cross.
"Our suffering is very small compared to others in the flood", he said. The music "put a personal face on the flood in a way that flood coverage doesn't, and I think that's why it's resonated."