The bicycle was black before it was white.

It lay on the pavement behind Alan Nakagawa’s house in Los Angeles’ Koreatown neighborhood. An English-style cruiser, it had fenders, a swept-back handlebar, and a wide leather seat. Nakagawa and two friends, Isaiah and Julio, got busy, pulling off the tubes and tires, disassembling the brakes, sanding the frame. Nakagawa is an artist who primarily works with sound, but on this evening his medium was paint—two cans of white Krylon ColorMaster. He painted the chain guard and then the frame. He waved the can to coat the fork, the handlebar, the saddle, the fenders, and the chain. Finally, Nakagawa painted the rims and the spokes and the pedals.

It was after dark now, and the bike was done, leaning against a couple of sawhorses, gleaming and wet.

Deborah Gresham was almost home from the store. It was after dark on a Friday night in October and she was riding her beach cruiser westbound on Cerritos Avenue, a busy road in Stanton, a small city located in the northern interior of Orange County, just a few miles west of Disneyland. This stretch of Cerritos Avenue is five lanes wide—two lanes in each direction and a center turn lane—and has a posted speed limit of 45 miles per hour. There is no shoulder.

At roughly 7:35 p.m., people who live nearby heard a terrible crash. Neighbors rushed from the dinner table to the street, expecting to see two cars smashed together in a smoking heap. Instead they saw a mangled bicycle sitting in the road. One of its wheels was detached and wobbling down the street.

There was a car, too. It was there for a moment and then it wasn’t, tail lights speeding down Cerritos Avenue until they disappeared.

Gresham was pronounced dead at the scene.

The following day, a story in the Orange County Register reported that Gresham had been killed by an allegedly drunk hit-and-run driver. The story quoted a spokesperson for the Orange County Sheriff’s Department who said that officers were dispatched at 7:41 p.m., that the suspect left the scene and was “eventually located at his residence in Stanton,” where he was arrested and charged with suspicion of felony DUI, vehicular manslaughter, and other charges. The story also named the suspect: Ricardo Sandoval Hernandez.

Hernandez was arraigned on October 19, posted a $130,000 bond, and was released. He appeared before a judge in a California Superior Court in the city of Westminster, where he was charged with four felonies and multiple enhancements. The charges included vehicular manslaughter with gross negligence, hit and run with permanent injury or death, and driving under the influence of alcohol causing bodily injury.

The court documents allege that Hernandez had a blood alcohol level of 0.18: California law sets 0.08 as the threshold for DUI. The complaint does not detail how much alcohol Hernandez consumed on the night he allegedly killed Gresham. But if the weight on his OCSD booking is accurate, it is not difficult to estimate a ballpark figure using online tools designed to help people calculate their BAC before they get behind the wheel. (The precise figures will vary from individual to individual.) According to multiple tools I used, a 280-pound man would have to consume about 13 and a half beers to reach a BAC of 0.18.

The crew meets at Danny Gamboa’s apartment in Long Beach. It is 8 p.m. on a Monday night, three days after Gresham was hit. I get off my bike, shut down my lights, and climb a flight of stairs to knock on the door.

Inside, they're gathered—Gamboa, Nakagawa, Terez Sanogo, and Kirstin Jensvold-Rumage. Danny pours each of us a glass of white grape juice and we make introductions. Everyone is friendly, but also cautious and restrained.

Gamboa is the cofounder of the Long Beach organization called Ghost Bikes, part of a loose nationwide network of groups that creates roadside memorials for cyclists who have been killed by cars and that otherwise advocates for awareness and cycling safety. If anyone who is riding a bike in Southern California—a region that stretches from San Diego through the entire Los Angeles metro area and up into the Central Valley; an area larger than New York State—is killed in a crash, Gamboa’s Ghost Bikes will respond. Sometimes the group even places bikes in communities in the Bay Area.

To cover so much geography, Gamboa and his partner rely on a network of two dozen regional volunteers to spearhead operations and line up additional manpower. In a past professional life, Gamboa supervised logistics in the trucking industry, so he knows how to manage this enterprise, but it wouldn’t succeed without committed volunteers. The guy who coordinates Ghost Bikes in Ventura County, Anthony Navarro, lost his 6-year-old child a few years ago—he was cooking a turkey on Thanksgiving morning when his son was hit and killed on a neighborhood street. Gamboa got involved in the ghost bike movement about six or seven years ago. “I got hit from behind in 2008 and after that I got involved in advocacy,” he says. “I started doing this and advocating for complete streets. And I’ll tell you, the more I did ghost bikes, the more I wanted to teach bike safety.”

The five of us climb into two vehicles to make the 20-minute drive to Stanton. As we get onto the freeway, I ask Gamboa how many ghost bikes he has personally placed. Through the end of October, at least 67 cyclists were killed this year by cars and trucks in Southern California. Ghost Bikes has set out a memorial for every one of them.

“Hundreds,” Gamboa replies. “At some point I realized it would be healthy to stop counting.”

Ghost bikes are nationwide now, but the phenomenon is relatively young. Back in 2002, an artist named Jo Slota had recently moved to San Francisco and took note of stripped and abandoned bicycles he saw chained around the city. “I was a full time commuter cyclist and these bones looked like some kind of urban road kill,” he tells me. “I decided to paint them as a means of recognizing them, and in doing so, give them a new appearance that seemed more appropriate to their current status in a discarded material lifecycle. They were bones, ghosts of something once active and full of potential.”

Over the next three years, he painted 23 bikes stark white. Throughout the whole endeavor, he wasn’t thinking about memorializing cyclists. “There were no ghost bikes in 2002,” says Slota, who presently works as a product development engineer at a high-end ceramics and housewares company. “I did this in a way that was more poetic than literal and intended to document the project and turn it into a coffee table book, some kind of portrait of urban living.”

Patrick Van Der Tuin had a more literal approach. It was late in 2003, and after seeing a car drift and rear-end a woman riding in a bike lane in his hometown of St. Louis, he decided to create something the driving public would take note of, something more provocative than a Share the Road sign. So he took an old bike and demolished as if it had been hit from behind. “We folded the rear wheel and wrecked the rear triangle,” Van Der Tuin says. He painted that bike white for functional reasons: “It was autumn and I wanted the bike to stand out during the day and at night.” He left a sign on the bike; it said “Cyclist Struck Here.”

A week later, Van Der Tuin and friends set out 15 more bikes around St. Louis. “People didn’t know what to think at first, but you could see that people were slowing down to look at them,” he says. Van Der Tuin called the project Broken Bikes, Broken Lives. And it got a lot of attention throughout St. Louis, though it hadn’t spread elsewhere yet.

That changed early in 2004 after Dirt Rag magazine wrote a story about Van Der Tuin and his white bikes. “Suddenly I started hearing that they were popping up in a bunch of U.S. cities,” he says.

Eric Boerer ran a recycled bike shop in Pittsburgh (where Dirt Rag is based), and he says some editors reached out to him to start a similar program locally. “I had access to a ton of messed up bikes,” Boerer tells me. He recalls how he and some friends coined the term “ghost bike.” “We got together to plan the project over some beers, and started brainstorming ideas and someone came up with ghost bikes, both for the obvious element, but also because it feels like we were like ghosts to drivers, like they don't really see us,” he says. “I don't know, we had a few beers.”

In 2004, they registered the web domain ghostbikes.org. And later that year, the Associated Press wrote a story about their work. Soon ghost bikes spread to New York City. A phenomenon was born. No one precisely tracks the number of ghost bikes nationwide, but multiple sources indicate that more than 1,000 of the memorials have been installed in 200-plus cities around the world.

Van Der Tuin, who presently works as executive director of St. Louis BWorks, a non-profit that gives free bikes to kids and teaches them maintenance skills, is amazed at how the practice has spread—he’s seen ghost bikes in Tokyo and rural Michigan and quiet corners of New York City. “I can’t say I’m proud because the whole thing is too sad,” says Van Der Tuin. “You see a ghost bike and then you know someone died there. People keep calling them accidents but most of them are crashes that could have been prevented. I’m glad people have taken up the fight to increase awareness but it’s hard not to get overwhelmed by the sadness.”

A few newspaper stories published the day after Gresham’s death offered some insight to her life and death. One mentioned that she had been the creator of a popular Facebook group called “Zombie Killers 2,” dedicated to the television show, The Walking Dead. That story indicated that the Gresham’s group had more than 20,000 members and that she had cultivated relationships with people all over the world who were die-hard fans of the wildly popular show.

I reached out one member of Zombie Killers 2, the Facebook group that Gresham had created and managed, and he put me in touch with an administrator who gave me permission to join the group. I wrote a short post, introducing myself and this story, and asking people to share stories about Debbie. Within 24 hours, more than 85 people had replied to the thread and many others contacted me directly. Other than one of Gresham’s five children, no one I communicated with had met her in person, but almost all of them seemed to know her well.

One man named Jim Campbell (who goes by the handle Hillbilly Jim) said that Gresham had “saved me from being homeless by selling my drawings on here in auctions.” Jim and others described Gresham’s constant efforts to raise funds for needy people and the local children’s hospital. “Her heart was very large,” he said.

Dawn Dutra described how Gresham had helped her during a hard stretch. “I went through a really tough time about a year and a half ago,” Dutra told me, describing financial hard times that led her husband to take a job in a different state and the family to be separated for four long months. “Debbie constantly messaged me to see how I was doing. She would talk to me for hours just to cheer me up.”

Amanda Voncille Gurkins described how Gresham helped her though the hardest stretch of her life, only six months after she joined Zombie Killers 2. “I miscarried twins. It was really tough physically, emotionally, and mentally,” she wrote. “Within four days of the miscarriage, I had one of my childhood friends die.” What followed was what Amanda describes as “the beginning of a breakdown,” but Debbie saw a comment on Facebook and shot her a message. “I was sitting on my bathroom floor alone in the house trying not to cry. She called me and sat on the phone with me for two hours while I cried.”

Sarah Medley considers Gresham one of her best friends. “We were both insomniacs and talked all hours of the night,” Medley wrote in a private message. “I’ve know her for a few years and it feels like I’ve known her all my life. She was the one I turned to in my time of need because she was always so incredibly soothing. She radiated kindness.”

Before long, I was connected on Facebook and Instagram to two of Gresham’s daughters. I watched from afar as they shared memories about their mother. One of them posted an image of the ghost bike that bore their mother’s name, writing that the family was thankful for the memorial. Eventually, I got the courage to write them and ask if they wanted to share any thoughts about their mother.

One of them, Sarah, messaged me a lovely tribute, one that documented her mother’s philanthropic efforts as well as her love of cola-flavored Slurpees and chocolate. She wrote that her mother was always wearing second-hand clothing so she could buy things for her four children. “She would also always put others before herself,” the young woman wrote. “She had a heart of gold when it came to people who needed help.”

I asked Sarah where her mother had gone on her bike that night. “She just ran out to the store,” she wrote. “She wanted to get drinks for my brothers and some cat litter.”

We park in a strip mall at the corner of Cerritos and Knott Avenues and start walking. Desvold-Rumage ducks into a 7-Eleven to grab a book of matches while the rest of us head eastbound on the sidewalk along Cerritos. Everyone is looking for clues; newspaper items about the incident lacked specifics about the crash site and no one came by during daylight hours to scope the site. We spend five minutes walking along the dark boulevard in silence as cars barrel by at highway speed.

And then we see flickering light up the street: a shrine. On the sidewalk outside a modest home sits a cross surrounded by flower bouquets and memorial candles. I had done some sleuthing on Facebook beforehand, and had stumbled upon a post from one of Gresham’s daughters mentioning that her mom had died very close to their home. I look down at the shrine and up at the house, windows drawn.

Through the end of October, at least 67 cyclists were killed this year by cars and trucks in Southern California. Ghost Bikes has set out a memorial for every one of them.

The burnt remains of signal flares sit in little mounds on the pavement. And as we walk further eastward, the edge of the street is increasingly littered with crash detritus: broken glass, scraps of metal, large strips of plastic. I kneel down to examine one little pile and something orange catches my eye—a plastic spoke reflector from a bike.

The crew huddles and decides to lock the ghost bike to a sign post near the apparent crash site, perhaps 60 yards east of the shrine. Though most families wind up expressing appreciation for ghost bikes, no one wants to traumatize relatives with a large and unexpected memorial on their doorstep. Desvold-Rumage snakes a short, heavy chain around the bike and the pole and locks it shut. She then lights five or six candles as everyone else shoots pictures and videos. Few words are spoken. I kneel on the sidewalk and try to imagine the moment Gresham’s family will see the memorial.

Stanton isn’t a bike-friendly city. According to Mike Wilkinson, a local who considers himself one of two active recreational cyclists in the area and who lives about a half-mile from where Gresham was hit, says Stanton has no more than a mile or two of actual bike infrastructure and that efforts to engage city officials on the issue have not been successful.

Earlier this year, the city of Stanton commissioned an 82-page Complete Streets Safety Assessment—funded by a grant from state and federal agencies and conducted by two researchers with the Institute of Transportation Studies at UC Berkeley. The document specifically mentions a stretch of Cerritos Avenue as a candidate for a road diet—concluding that the roadway could still handle the existing daily traffic of 13,000 to 15,000 cars per day if a bike lane was added in each direction. But in the report, the authors comment that this project would not be added to their suggested list of projects because city officials told them that Stanton would lose so-called Measure M funding if they pursued a road diet.

Like many communities, Stanton needs all the external tax funding it can get. So taking care to not lose Measure M funding—a countywide sales tax that has generated more than $5 billion for road projects in the past two decades—makes some kind of sense. Though the eligibility requirements for the program were rewritten this past April and now state that local jurisdictions must consider planning strategies “that accommodate non-motorized transportation,” the document clearly states that funding would be cut if traffic calming measures are pursued on “secondary arterials” like Cerritos.

The lack of quality cycling infrastructure in Stanton is hardly isolated. While many of the affluent communities in southern and coastal Orange county have terrific networks of bike lanes, huge swaths of the county, which has more than three million residents, still lack the most basic exoskeleton of safe places to ride. The same could be said for Los Angeles County, where I live, and many communities around the United States.

I ran into this first hand when I rode to meet Gamboa and his crew. I decided to leave work in Los Angeles that evening and ride my bike to catch a light-rail train to Long Beach—a Metro station is located three miles from Gamboa’s apartment. I had never ridden in his neighborhood, but Google Maps suggested a bike route and I knew that Long Beach has been highly ranked in all of the most prominent lists of America’s top cycling cities.

I have ridden in Long Beach before—the network of bike lanes downtown and near the beach is great—but my ride to Gamboa’s house was a genuine terror. I rode eastbound on Del Amo Boulevard, as Google had recommended, first on a narrow shoulder and then on a sidewalk, and then on a dirt footpath. And then there was nothing, right where the roadway reached Interstate 710—a stretch with heavy truck traffic that is poorly lit and has no shoulder, lacking proper crosswalks or consistent sidewalks. I just grabbed a lane on a dark virtual highway and sprinted for 60 seconds.

It was as though engineers or politicians had decided that no sane person would want to walk or ride a bike from a Metro station to a residential neighborhood a half-mile away. Later in the evening, I asked Gamboa if there was a better route from the train station. He said there was not.

The ghost bike is locked to a signpost, candles are lit, and the crew is documenting the memorial with photography and video. Up the street, I notice that someone is on the sidewalk, attending to the shrine.

I ask Gamboa about what he does with all the pictures and video he shoots when he’s out installing ghost bikes. “Part of it is to have a record of the memorial and part of it is that the bikes themselves are beautiful,” he says. “But part of it is just a mechanism to deal with the dark nature of what we’re doing. I think if I didn’t partially treat ghost bikes as an art project that I would need regular therapy.”

A woman named Leslie is on her knees, relighting memorial candles that have been extinguished by the wind. Leslie has lived in the neighborhood for almost 20 years. She says she grew up in El Salvador and Guatemala. She saw Gresham on walks and bike rides many times. “I know she had an English accent,” Leslie says, noting that she and Gresham exchanged smiles over the years but never had a conversation. “I guess you could say it’s a cultural thing.”

Leslie was at home alone when she heard the crash. She rushed to the corner and saw the bike. “My first thought was that it might be my son,” she admits. “It took courage to look up the street. I saw things growing up in Central America, and now I have seen things right here on this street.”

Leslie points way up the street to a traffic light at the corner of Cerritos and Knott Avenues. It’s about a third of a mile away. She says everyone in the neighborhood makes their kids walk to the light if they want to cross Cerritos. It takes about 20 minutes to safely cross the street.

I walk with Leslie down the ghost bike, and she asks about its meaning. “It’s a memorial,” says Gamboa. “We want to honor the cyclist who died. We want people to slow down and realize what happened. We want people to see beauty.”

Leslie nods her head, and then points out Gresham’s house—it is directly next to where the ghost bike is locked. There is a moment of confusion. I ask her about the little house up the street, the one with the shrine out front. Leslie takes a couple deep breaths. She points to the shrine. “That is where the body came to rest,” she says. She starts to cry quietly. “That is where most of the body came to rest.”

Gamboa and Nakagawa and Sanago and Desvold-Rumage unlock the ghost bike and move it closer to the shrine. Desvold-Rumage leaves the key on the cross. “If you see the family, please show them this key,” she tells Leslie. “That way if they want the bike removed or want to keep it, they can.”

Leslie asks me if I believe in God and I shrug back at her. “I used to be a Catholic and now I’m not,” she says. “But I still believe in God and certain things. I have to believe that this woman is in a better place.”

The ghost bike crew takes a final round of photographs and talk with Leslie, and I walk back down toward the crash site. I follow the trail of debris until it ends, right where Leslie said the impact occurred. The spot is directly beneath a street light casting an orange glow on the road. I can see faded chalk on the street; little piles of extinguished signal flares. Cars race by.

Gresham could see her driveway where she was hit. Even on a beach cruiser, her ride would have been over in five or 10 seconds.

Gresham was killed nine days before the season premiere of her favorite show. She and the 20,000-plus followers of her Facebook group had spent the entire summer and early fall talking about the highly awaited episode. Everyone knew that a key character would die in the opening episode.

Most threads on Zombie Killers 2 were a memorial to the woman who had launched the group. People said they were trying to email the show to see if a tribute to this super-fan could come together. A couple of people messaged me privately to see if I could help. (I work as an editor at The Hollywood Reporter.)

I shot off a quick email to two publicity executives at AMC, the network that airs The Walking Dead, including links to some news stories about Gresham’s death. One of them wrote me back almost immediately, conveying shock and vowing to forward it to producers. No other promises were made—it was the frantic week before the most important premier in the show’s history.

On Sunday October 23, the episode aired, with the characters Abraham and Glenn dying in graphic fashion. At the end of The Talking Dead, a live television aftershow that airs after each episode, the screen turned blue and a message appeared: “In Loving Memory of Deborah Gresham,” it said, “A huge fan forever in our hearts.”

The explosion of emotion on Zombie Killers 2 was palpable. One of Gresham’s daughter posted a message after seeing the tribute. “I'm so happy to have seen this,” she wrote. “I'm sure my mom is very happy in heaven right now seeing this.”

Due to the flurry of curious Googling that the tribute generated, more than 2,000 people joined Gresham’s group in the following week.

I return to the site of the crash on a Saturday afternoon, 15 days after Deborah Gresham died. The ghost bike is still there, adorned with some red plastic flowers and a Walking Dead wristband, from one of Gresham's favorite shows. The shrine is still there, too—a few memorial candles are still flickering, and people have scribbled messages with chalk on the sidewalk. Cars are still hurtling past.

I walk around the neighborhood, knocking on doors and asking questions. Everyone heard the crash and no one had ever talked with Gresham. People tell me that a fire truck was the first emergency vehicle to arrive, that police were on the scene with the street closed until 2 a.m. One woman walks out to the curb to show me the exact spot where Gresham’s shoes wound up on the street; how the police drew chalk around them.

I stand directly across the street from the ghost bike, a memorial to a woman who went out for cat litter and soda and was killed seconds from home. In this moment, at least, no one appears to be slowing down as they drive past.

As I stand there, I think about how Gresham’s daughter, Sarah, expressed her sense of loss in a message. “I am sad that she is gone,” Sarah said. “She was the life of my family and now that she's gone it's really quiet and feels like we are missing an important piece to us. It's lonely without her.”

The moment ends as two teenaged girls walk past, chatting loudly. I ask them if they saw anything, and one suggests that I talk to her grandmother. She runs into the house, and a few minutes later emerges with a woman who appears to be in her 60s. This woman, who asks that I not use her name, doesn’t speak any English. So her granddaughter starts translating. A swarm of children form around us.

“We heard the first crash and then another a second or two later,” she says. “So we ran out here to the street. My boyfriend kept trying to cross the street to reach the woman but the cars wouldn’t slow down. He almost got killed trying to help her.”

She says a sentence or two in Spanish and points across the street at the ghost bike. I glance at her granddaughter. “She says part of her would like to forget what she saw but that white bicycle keeps reminding her,” the girl says, turning her head to hear and translate what the woman says next: “A woman died right there, right in front of her own house. How can you ever forget a thing like that?”