BOULDER — Four young friends set off from a birthday party in the craggy hills near northwest Boulder late Wednesday, thunder clapping and rain pummeling their little silver Subaru.

In the driver’s seat, Emily Briggs panicked. Water, rocks and mud were rushing down narrow Linden Drive, slapping against the car and flooding the steep, winding two-lane road.

So 19-year-old Wesley Quinlan took the wheel, and the group — Emily, Wesley, his girlfriend Wiyanna Nelson and Nathan Jennings — forged on. But farther down Linden, they found themselves in a mudslide that crumbled driveways and flipped a Jeep onto its roof.

They were stuck.

Soon, three of the friends would climb out of the car to get to safety. Only one would make it. By Friday afternoon, crews searching with dogs had discovered two of their bodies.

Authorities, neighbors and Wesley’s mother described the terror, anguish and chaos of that night.

As the rain began pounding in Boulder, mother Glenda Aretxuloeta couldn’t help but worry. She texted her son and Wiyanna, pleading with them to go home soon and stay safe.

It was about 11 p.m. when Wiyanna replied last, assuring her that they were getting ready to go home.

They made it as far as Linden Drive and South Cedar Brook Road before the Subaru became stranded in the torrent, behind the overturned Jeep. What happened next isn’t entirely clear, but Aretxuloeta said Nathan was the first to leave the car, followed by Wiyanna and Wesley.

The swirling water and mud quickly swept away Wiyanna and Wesley.

His friends out of sight amid the crushing floodwaters and blinding rain, Nathan clung for his life to the Subaru’s side mirror. He held on so tight it ripped off in his hands. He frantically grabbed onto branches.

A third car rolled upon the scene carrying Andrew Slack, a volunteer firefighter equipped with a radio and little else.

Slack jumped out and struggled to pull Jennings from the quickly rising rapids and mud. Together they scrambled up a hill to Dennis Giannetti’s door.

“They showed up covered in mud and pretty much in shock,” said Giannetti, who, along with his wife, Terri, had awakened to the flashes of lightning and rain beating against his house.

“Nathan was just hysterical,” Giannetti said. “I’ve never seen anyone covered head to toe in so much mud.”

Nathan was frantic, believing his friends had been swept away. The group called authorities for help.

The Giannettis gave the exhausted strangers food, showers and blankets while they waited. From the picture window in their living room, they looked down below on the floodwaters and the Subaru.

About 40 minutes later, the blare of a car horn startled them.

“Nathan said, ‘It’s got to be Emily! She’s still alive in there,’ ” Giannetti said.

Emily had remained in the stranded Subaru while her three friends disappeared in the dark and chaos.

Slack and another neighbor, who had sought aid for his nine-months-pregnant wife, rushed down the hillside and into the muck.

Emily was OK.

“Emily was so excited to see Nathan, the two of them just embraced for 10 minutes, crying in each other’s arms,” Giannetti said. “They were shaking, they were so cold and frightened.”

By 2:30 a.m. Thursday, Aretxuloeta got a phone call from Wesley’s father, who had been told by one of the other families that their kids were in trouble. They contacted authorities and prepared for a search.

“As soon as the sun came up, in momma-bear fashion we went up to search for them,” Aretxuloeta said.

Across Linden Drive, Andria Lewis also got a stir early Thursday. She and husband, Burt, emerged from their home to check out the damage and saw a group of strangers huddled under an umbrella.

“They kept saying, ‘Our son’s missing, our son’s missing,’ ” the downpour drowning out their voices, Lewis said. “I just said, ‘What can I do?’ They’d been out there for hours.”

She led them inside, where they shared prayers and lit a candle.

Wesley was missing, and searchers had found Wiyanna’s purse near the Lewis’ home.

The morning wore on, and Wesley’s family sat vigil in the Lewis’ home. About 11 a.m. Thursday, authorities told them they’d found his body. Deputies had relied in part on photos his parents had brought with them.

“I doubled over and just felt a surge of emotion,” Aretxuloeta said.

Back at the Giannetti home, Nathan and Emily faded in and out of sleep. They stayed there much of Thursday, discussing the events in fits and starts.

Slack, the firefighter, also remained at the house for several hours, gazing out the window, not saying much at all.

As rain continued to fall on Thursday and into Friday, emergency crews pressed on with the search for Wiyanna along Linden Drive.

By Friday afternoon, they announced that they had uncovered her body, not far from the Subaru and the spot where Wesley was found.

Just one week earlier, Wesley and Wiyanna, 19, had joined Aretxuloeta on a vacation in Santa Fe, where they all basked in hot springs and stared at the stars.

The road trip was an early celebration for Aretxuloeta’s birthday, and a chance for Wesley to introduce Wiyanna to his Native American roots.

“He was very very connected to my Native American heritage,” Aretxuloeta said.

A recent Centaurus High School graduate, Wesley had just been accepted into the Colorado Film School.

On the drive Aretxuloeta and Wesley talked about his next film ideas — a passion he had since age 5, when he would take any camera he could get and film short videos, she said.

“Oh, my gosh, he went on and on, he was so excited,” Aretxuloeta said.

Wesley, who was born and raised in Boulder, had his first date with Wiyanna on Valentine’s Day, but already the two had grown close. A Facebook photo shows a smiling pair, Wiyanna’s chin resting on Wesley’s shoulder.

“They were such a cute couple,” Aretxuloeta said.

Sadie Gurman: 303-954-1661, sgurman@denverpost.com or twitter.com/sgurman

Help for flood victims

In the wake of torrential rainstorms that have raked the Front Range, flood victims can draw some comfort in knowing there are organizations offering help. Along with opening a number of temporary shelters in Boulder, Larimer and Adams counties, the American Red Cross in Colorado is collecting donations to underwrite relief efforts. redcross.org/charitable-donations.

“The best way to help out is with cash donations,” said Patricia Billinger, communications director for the Red Cross in Colorado and Wyoming. Even a little bit helps. A $2 donation will pay for a snack, $2.50 underwrites a hygiene kit distributed to evacuees, while $10 will pay for a hot meal and a couple of blankets, Billinger said.

The Intermountain Salvation Army also is working on flood-relief efforts. Their donation website is imsalvationarmy.org.

William Porter, The Denver Post