With tragedy comes an inevitable question. Why?

Not just why a fire started on Dec. 2 and consumed a ramshackle artist collective in Oakland called Ghost Ship, or why 36 people attending an electronic music performance there lost their lives.

But why they were there, together, in that place and at that time. And why others lived.

Organizers announced the clandestine event at least a week in advance, but gave no more than a few days’ notice about where it would be held. Yet dozens of young artists and intellectuals found the place, drawn by the transformative thrum of electronic music, of dancing as one, and the chance to experience a world on the edge.

Alex Ghassan, a filmmaker, came with his fiancee, who had just moved to Oakland, to show her an offbeat slice of the city. Laura Hobbs met up there with a roommate who was thinking of joining the group of artists who worked in the warehouse. Musician Ben Runnels, a.k.a. Charlie Prowler, headed over with his bandmate to see friends perform. Like Runnels, Jonathan Bernbaum showed up because that was his life: the people, music, and electronics happening at Ghost Ship that Friday night.

Different paths, all converging in a catastrophe that would unfold in the hour before midnight.

Jonathan Bernbaum texted his friend Jay Fields at 8:45 p.m. urging him to attend the show at the warehouse in Oakland’s Fruitvale neighborhood. Golden Donna 100% Silk, an act from Madison, Wis., was headlining. But the real draw, Bernbaum said, was their friend Barrett Clark, who was doing sound.

The three men — Fields, an electronic musician; Clark, a sound man; and Bernbaum, 34, who traveled the world doing lighting and computer visuals for the Australian electronic dance music duo Knife Party — were part of a nearby artist collective called Katabatik.

Clark “had the best, biggest, loudest sound around the bay — and he was the nicest dude. The most generous,” Fields said.

Clark handled sound for some of San Francisco’s biggest dance clubs. But he also took small, esoteric jobs because he loved making smaller artists sound big. That was his generosity, Fields said, and artists thanked him for his gift of loud.

As for Bernbaum, his genius — his wizardry — lay in his ability to create light shows that interacted perfectly with artists’ vibrating music. He’d been doing it only five or six years, but his passion and a master’s degree in film editing had propelled him quickly from novice to internationally recognized expert in the growing field of electro-dance visuals.

Yet it was the underground arts culture celebrated at places like Ghost Ship, not the commercial music business that handsomely paid his bills, that kept Bernbaum grounded and happy. He rarely missed an event if he was in town.

Still, Fields was reluctant to go. Like a lot of people, he said, “we thought (Ghost Ship) was not a responsible space. It was unsafe.”

Despite his misgivings, Fields promised Bernbaum he’d be there. “This is our family. These are our people,” he said.

As he and Bernbaum negotiated by text in Fruitvale, over in West Oakland, Jennifer Kiyomi Tanouye, 31, posted on Instagram: “Doing nails in a rave cave tonight at the Ghost Ship!” Tanouye, a manager at the music-recognition app Shazam, loved taking her pop-up Underground Nail Bar to events and parties around the Bay Area.

In Berkeley, Laura Hobbs was working late at a think tank for clean energy. Electronic music was not her metier, but she was heading to Ghost Ship that night to connect with her roommate, Claire Rosenfield, who was thinking of joining the artist collective there known as Satya Yuga. Its members built structures of reclaimed wood for Burning Man and other festivals and kept workspaces on the first floor of the warehouse.

“As a way to support her and the community, I went,” said Hobbs, 24, who was interested in seeing the storied space for the first time. She would also meet a second roommate, her cousin Alastair Boone, at the warehouse, as well as Rosenfield’s boyfriend, Conner Smith.

Still dressed in her work clothes — a maroon turtleneck, black pants and a large, flowing scarf with a mushroom design — Hobbs; her boyfriend, Michael Rosen; and another friend, Seung Lee, tried to get to the show before 11 p.m., when admission would flip from $10 to $15.

They were nine minutes late. Slipping past five or six people smoking around the entrance, they approached a guy in a slapdash ticket booth. Could they still get in for $10?

No problem. Another guy in the booth marked their hands with a black Sharpie, and they went inside to find their friends.

Alex Ghassan initially wasn’t sure about his plans for the night. A 35-year-old filmmaker who often worked in hip-hop — producing videos for rapper Skyzoo and other notables — electronic dance music wasn’t really his thing. Earlier that evening, at Oakland’s First Friday festival downtown, a friend had texted to see if he wanted to go to another party in the hills.

But Ghassan’s fiancee, Hanna Ruax, 32, had just moved from Helsinki to be with him, and he was eager for her to explore Oakland’s cultural offerings. Ghassan was comfortable anywhere, with anyone.

The independent film producer, who had arrived from the New York City area two years before, was known for his work portraying the lives and struggles of those on the fringe. He was shooting video for the public television station KQED, and recently had finished three films about artists and minority communities for the Oakland Museum of California.

His current project was a documentary on Bay Area homelessness.

Ever the filmmaker, Ghassan posted a shadowy video of the scene at Ghost Ship on Instagram before most people arrived.

Driving his old blue Honda with band memorabilia strewn across the dashboard, Ben Runnels picked up his musical partner Nicole Siegrist, who went by the name Denalda Nicole Renae. The two architects of technopop were inseparable.

Runnels, 32, and Siegrist, 29, had recently released their first recording together under the band name Introflirt. They were hoping to play their own shows soon and had already booked two gigs for the coming year.

The duo’s music blended 1980s New Wave sounds — similar to Depeche Mode or the Cure — with classic jazz standards. It was unique, and they’d coined a new term for it: “croonwave.” Much of the music was made using a synthesizer that Runnels’ parents bought him when he was just 4 years old.

Carving out a new musical genre was an unexpected trajectory for a man who’d been valedictorian at Southern Vermont College and had graduated with a degree in communications.

There was no way the two were going to miss that night’s show. Runnels’ roommate, Johnny Igaz, a.k.a. Nackt, was DJing, and a collaborator, Chelsea Faith Dolan, known as Cherushii, was on the bill with Golden Donna. Siegrist’s roomate, Donna Kellogg, would also be there. So would another colleague and musician, Travis Hough — a.k.a. Travis Blizten of Ghost of Lightning.

Siegrist had shared a post about the clandestine event a week earlier — and now the plan had come together.

If the vibe for the show was meant to be earsplitting or otherwordly, it hadn’t happened by 11 p.m. No smell of tobacco or marijuana thickened the air. No synthesizer forced anyone to shout to be heard.

Instead, a slow-tempo digital mix with a loud bass drum wafted down from the second-floor performance space and permeated the artists’ nooks on the ground floor below, where people may or may not have been working or hanging out. It was impossible to tell just by looking out across the mazelike room.

Those arriving for the show found an environment that was part museum tour and part tea party. While members of the Satya Yuga collective showed off their large art pieces just outside the first floor, a few dozen people settled into chairs and sofas on the second floor and bobbed to the music.

After locating her roommates, Hobbs went with Rosen and Lee to hunt for the makeshift staircase leading to the second floor, a narrow set of steps tucked against one wall. They felt unsteady as they climbed single file up four or five wooden steps to a landing, took a right turn up a ramp to another landing, then stepped up a final set of planks.

Purple and blue lights greeted them, intensified across the large living-room-like area by a pair of room-divider screens beside the booth where Nackt was DJing. Clark was on sound. In another corner, fingernail artist Tanouye sat painting designs on a woman’s nails.

Bernbaum was there, too, and feeling relaxed. He was thinking of a friend in Kentucky, a production assistant who loved touring with bands so much that she often felt down after returning home. Since she hadn’t replied to his “where are you?” text a few hours before, he figured she needed cheering up. At 11:13, he sent her a cute video of a sugar glider, a tiny marsupial, flying across a room.

Hobbs and her friends took in the scene but lingered only a few minutes before heading back downstairs and outside to find a convenience store.

They returned a few minutes later with three beers.

Hobbs was about to go back inside when she noticed smoke pluming from the second floor and a crowd gathering across the street. The building didn’t appear to be on fire, but the black cloud was surreal enough to stop her.

She pulled out her phone and called 911 — but hung up when she heard sirens. The time was 11:25.

A woman stumbled out of the warehouse, dropped to her knees and began to wail. Suddenly, a firestorm appeared to be collapsing the building. As firefighters arrived, they heard screams from inside.

Jay Fields had just reached the scene. His friends, Bernbaum and Clark, were still inside.

So were Ghassan and Ruax, Runnels and Siegrist. And so many others.

In her final moments, Siegrist texted her mother. “I’m going to die now.”

Hobbs, still with Rosen and Lee, couldn’t imagine her cousin and their other friends trapped inside. Just as she punched in Boone’s number, a call from her cousin appeared on her phone.

“Are you with everyone?” Hobbs demanded. She was. Boone, Rosenfield and Smith had wriggled out of a gate on one side of the warehouse, frantic in their belief that the others were still trapped inside.

Reunited, the six collapsed into each other. In silence, they watched the building go up in smoke and flames.

Nanette Asimov and Kurtis Alexander are San Francisco Chronicle staff writers. Email: nasimov@sfchronicle.com, kalexander@sfchronicle.com Twitter: @NanetteAsimov, @KurtisAlexander