Brittany Phillips was an 18-year-old student in Tulsa, Oklahoma, when she stopped showing up to class, arousing suspicion among those who knew her.

She was last seen dropping a friend off at home after 8 p.m. on September 27, 2004.

Three days later, on September 30, officers responding to a welfare check – after a concerned friend contacted authorities – found her strangled body in her second-floor apartment. She had been sexually assaulted.

In the two decades since, ex-boyfriends and strangers have been questioned, sex offenders investigated and DNA swabbed – but there is still no suspicious.

“This is the first anniversary where the case has been colder than when she was alive, because we buried her on her 19th birthday, October 4,” said her mother Maggie Zingman, 69. , to PEOPLE. “I never thought she would be murdered. But I never thought it would be a closed case. And then I never thought I would be sitting here on the 20th anniversary.

This year, as she has for 18 years, Zingman is traveling the country in her bright purple and pink KIA Carnival, adorned with large photos of Brittany and a number to call for advice.

His goal? Drawing attention to her daughter’s case in hopes of finding the killer.

Zingman, a trauma psychologist who works with veterans, dubbed her cross-country forays: “Caravan to Catch a Killer.”

“I want my daughter’s case to be solved before she dies,” she said. “I feel like the business dies with me. Brittany would kill me if I stopped, and she would do the same for me.

A student who loved sports

Brittany, a student at Tulsa Community College, loved sports and music and planned to transfer to Oklahoma State University and continue her degree in chemistry. She hoped to pursue a career in cancer research.

The last time Zingman spoke to her daughter was on Monday, September 27 – the same day she was last seen dropping off her friend – when the teen had to go to the care of emergency due to allergy problems.

“She had gone to the doctor because she was still having allergy problems and she couldn’t go in,” she said. “She was with a friend and she said to me, ‘I’m going to drop my friend off and then I’m going home.'”

Want to stay up to date with the latest crime coverage? Register for PEOPLEThe free True Crime newsletter for breaking crime news, coverage of ongoing trials and details of intriguing unsolved cases.

When Brittany didn’t show up for class, a friend called the police.

Inside the apartment, officers found Brittany dead on the floor next to her bed.

“There were defensive elements under the nails,” says Zingman. “She had to fight. I think maybe he was waiting there, or maybe he broke in after she was asleep.

Although he interviewed hundreds of people, “no one was really able to give anything concrete at the time this happened,” said Tulsa Police Department Detective Jeremy Stiles .

“Maybe he’s a serial predator.”

In 2007, with no suspect in sight, Zingman began to wonder if the killer had moved and was killing elsewhere. “Maybe he’s a serial predator, maybe he’s traveling the highways and he’s killed or raped people across the United States,” she said. “I really wanted to see if there were any similar murders. Maybe a spouse, a sister, a detective would hear something familiar in my story.

“I had this idea if I had something on the side of my car, something that people could see and automatically try to look me up and give me advice, maybe it would be a way to get the word out history across the United States.” she said.

Over the past 18 years, she has traveled more than 300,000 miles across 48 states, handing out flyers at rest stops, police stations and in traffic jams.

She crossed four vehicles, had car breakdowns in Oklahoma, Texas and Wisconsin, got lost in the middle of the night in Wyoming, rolled down a mountain in Utah in a violent rainstorm and sailed in icy conditions in Washington state.

To pay for her travels, she lived without heat, water and air conditioning, struggled to pay one salary after another and was already in debt. She says she has spent around $120,000 in her quest for justice for Brittany.

“It was worth it, especially in those early years, because I would get 12 to 16 (newspaper) articles every time I went out, and I went out twice a year,” she said.

His caravan trips generated multiple tips.

Stiles, the investigator, says, “We’ve definitely had people contact us and say, ‘Because of Dr. Zingman, that made me want to contact you and here’s what I know,’ or ‘Did did you check this? “or whatever.”

Stiles adds, “I have yet to meet a victim’s family as determined as Dr. Zingman, and she is doing an incredible job getting the story out and getting as many eyes and ears as possible.”

For Zingman, traveling on the road was a way to cope with his grief.

“That’s how I survive, because beyond the goal, the gifts, the connection, the hugs, the people honking at me while going down a mountain,” she says. “I’ve had such incredible experiences. I couldn’t have survived this without these experiences.

Although she remains hopeful that one day her daughter’s killer will be caught, her travels have become a way to connect with other families of unsolved homicides.

“It’s not really about my daughter anymore,” she said. “It’s really about wanting to reach out. Let me help you be a voice. Let me just tell you, you’re not crazy. Because that’s what kills people.

A trick complicates the timeline

A possible lead in her daughter’s murder surfaced in 2023 when Zingman received a call from her ex-husband, who told her he had found a birthday card that Brittany had mailed to him in 2004 to pass it on to his grandfather. The card was postmarked September 29 – two days after police believed Brittany had died.

“It was a stamp bought at a newsstand,” says Zingman. “If it was a regular stamp, it would be easy. Yes, it sat in the mail bin for a while, but it was printed by the newsstand. This stamp bearing this date could change the timeline.

Stiles agrees that the timing is peculiar, saying it’s “after what the detectives more than likely thought the incident would have happened.”

Stiles adds: “I can’t say 100% what I think about it yet, but it’s unexpected and strange.”

For now, Stiles hopes that current genetic genealogy work on the DNA found under Brittany’s fingernails will provide answers. “Obviously, if it leads to an individual, that’s certainly someone we’ll want to talk to next and understand how they were involved,” he said.

Meanwhile, Zingman prepares for his next road trip around Thanksgiving.

It plans to hit Texas, Arizona, New Mexico, Nevada and California.

“She was beautiful and intelligent, and it breaks my heart that the world lost her,” Zingman says. “But my car was the gift. I know millions of people know her, because millions of people have seen her on the road.

If you have any information about the murder of Brittany Phillips, please call Tulsa Crime Stoppers at 918-596-COPS or email [email protected].

If you or someone you know has been sexually assaulted, please contact the National Sexual Assault Hotline at 1-800-656-HOPE (4673) or visit rainn.org.