I spent years covering a serial killer. There's one answer I still want to find.

AUSTIN – A 12-person jury in San Antonio in 2022 took just five hours to end one of the most nefarious chapters in Laredo’s history.

Four years earlier, a serial killer had brutally murdered four women in the outskirts of Laredo. All of them were marginalized sex workers with substance abuse disorders. All of them were also women with siblings and parents and friends who loved them.

Over the span of 12 days, a man picked them up, one by one, drove them to remote rural roads and shot them in the head with a .40-caliber handgun.

Throughout that same time, a U.S. Border Patrol supervisory agent named Juan David Ortiz went to his job each day at the Joint Intelligence Center at Border Patrol Laredo Sector’s headquarters.

Ortiz, an Iraq War veteran and longtime agent, was married, with three children. From the intelligence center, he could keep tabs on regional police operations and the unfolding investigation of the serial killings.

After the serial killer pulled his gun on a would-be fifth victim, who escaped his clutches and notified police, investigators drew closer to the killer. Soon, they made an astonishing discovery: The man they were chasing was Ortiz.

He was committing the shootings with his agency-issued .40-caliber. When police took him into custody, he confessed that he had planned to keep killing.

After the verdict was read in December 2022, a judge sentenced Ortiz to life in prison without parole. In May, an Appeals Court in El Paso upheld the ruling, sealing Ortiz’s fate. He would spend the rest of his days in a Texas prison.

It would seem the story ends there. But tales like these don’t leave quietly.

I spent five years interviewing more than 300 people, poring over 1,000 documents and driving more than 9,000 miles around Texas to try to better understand the events of September 2018 in Laredo.

I spent hours, day after day, year after year, with victims’ families, in their homes and in courtrooms, learning about the women – Melissa Ramirez, Claudine Luera, Chelly Cantu and Janelle Ortiz – about their struggles and dreams. I interviewed investigators who pursued the killer and prosecutors who tried him in court.

The book that ensued – “The Devil Behind the Badge,” published by Dey Street/HarperCollins – comes out Aug. 6.

Exclusive: How borderland detectives first discovered Juan David Ortiz's serial killings

I wasn’t alone. NBC’s "Dateline," ABC’s "20/20" and Max’s "Homicide Hunter: American Detective" all produced features on the case, interviewing family members and detectives. The podcast "Gone South" made a six-episode series on it.

In a world full of tragic killings, why all the national attention and why a book now? The answer is both simple and infinitely complex. This case was by far the most intriguing, surprising and challenging story of my 20-plus-year career as a journalist.

Families of victims still hurt, but try to heal

In the four years between Ortiz’s arrest and his verdict, the victims’ relatives moved, grew families of their own and tried to reconcile lives without their mothers, sisters and daughters. Ciara Munguia, 26, Luera’s daughter, had a baby, Londyn, in that timespan. In one of the more ironic twists of the saga, Munguia now works as an intel analyst with the Webb County Sheriff’s Office – the agency that pursued and captured her mother’s murderer.

For the first few years after the murders, Munguia struggled with the hate and anger that consumed her over her mom’s killing. Slowly – especially after having Londyn – those jagged feelings began to recede. The trial and verdict were, in many ways, a huge step toward closure, she said. At the trial, Munguia met and chatted with Ortiz’s mom. The two hugged. Munguia cried.

Now, Munguia celebrates her mother twice a year: with a cake in December for her birthday; and with balloon releases each September on the anniversary of her death. Luera, who struggled with heroin addiction for years before she was killed, is in a better place now, she said.

“I wouldn’t be who I am if it wasn’t for her,” Mungia said. “I feel like she’s still all around.”

How did Juan David Ortiz murders affect Border Patrol?

One aspect that remains a mystery is what lessons, if any, Border Patrol learned as an agency from the Ortiz murders. Internal documents I obtained showed there was very little in his official file that would have alerted the agency to his actions. But colleagues and friends noticed a steep decline beginning around February 2018.

Ortiz, a Navy corpsman – or medic – and Iraq War veteran, suffered from PTSD and was prescribed a cocktail of psychotropic medications. He mixed those meds with copious amounts of booze. He complained to a therapist about nightmares, paranoia and suicidal thoughts. He bragged to colleagues that he knew where the sex workers dwelled along Laredo’s San Bernardo Avenue.

None of his spiraling behavior appears to have made it into Ortiz’s official Border Patrol record.

In the wake of Ortiz’s arrest, Border Patrol officials were quick to point out that his actions were not representative of the nearly 20,000 agents employed at the federal law enforcement agency. Yet that same year – 2018 – Border Patrol’s Laredo Sector alone saw two of its agents (including Ortiz) investigated for murder while off-duty and one for the shooting death of an unarmed migrant while on-duty.

In recent years, the agency has made important strides toward improving transparency and shaking a historic culture of impunity, including rolling out body cams on agents and publishing Discipline Overview reports on its website, which shows disciplinary actions taken on agents (albeit without any identifying details). Still, immigrant advocates complain the agency is not doing enough – and agents continue to get away with wrongdoing.

As we near a presidential election, border security will become an increasingly important topic and how the agency polices its own agents will be equally scrutinized.

What effect, if any, did the Ortiz shootings have on the agency? Unclear. Border Patrol officials declined to talk to me for the book or answer various Freedom of Information Act requests I filed over the years, claiming the issue was still under internal investigation – even long after their own agent had been arrested and charged.

A mysterious message

Most glaringly, Ortiz’s motive remains elusive.

One of the few clues Ortiz offered was during a nine-hour videotaped interview he had with investigators after his arrest, where he at first denied knowing any of the slain women then slowly admitted to the crimes in startling detail. As Webb County Sheriff Deputy Federico Calderon and Texas Ranger E.J. Salinas leaned in from across a table in the interview room, Ortiz described how – after killing his first victim, Melissa Ramirez – he was gripped by an urge to continue targeting sex workers.

“This is going to sound stupid,” he says in the video, looking down at his hands, “but I wanted to clean up the streets.”

Ortiz’s targeting of marginalized sex workers is not outside the norm for serial killings. As of 2018, FBI data showed women accounted for three-fourths of the 1,398 known serial homicides in the U.S., according to a study by sociologists Jooyoung Lee and Sasha Reid. And female sex workers are 18 times more likely to be targeted.

But what, specifically, made Ortiz turn from family man and Border Patrol rising star to serial murderer, seemingly overnight? And why did he target these women specifically?

Calderon, who spent 12 days hunting Laredo’s serial killer and was Ortiz’s lead interrogator during the confession, knows more about the case than arguably anybody else. Why Ortiz did what he did remains a mystery even to him.

“The only person who really knows is Juan David Ortiz,” he told me later.

After his arrest, I mailed several letters to Ortiz requesting an interview as he awaited trial at the Webb County Jail. He didn’t answer any of them.

Six months after the trial, in May 2023, after Ortiz was transferred to the Ramsey Unit, a Texas prison located in Rosharon, Texas, messages from him suddenly emerged in my inbox of an online network used to communicate with inmates. After an initial inquiry, he followed up, alleging a string of wrongdoing at the Webb County Sheriff’s Office.

Then, earlier this month, another message popped in from him.

“If you are willing – promptly schedule an interview,” Ortiz wrote, saying he preferred no cameras or recorders. He added, “Please understand that there is stuff that I'm simply not going to talk about.”

I agreed to no camera but told him I would need a recorder to accurately capture our conversation.

He has not yet replied.

Jervis is an Austin-based national correspondent for USA TODAY. Follow him on X: @MrRJervis. His book, "The Devil Behind the Badge," which details the 2018 Laredo serial killings, will be released Aug. 6. 

This article originally appeared on USA TODAY: Border Patrol serial killer Juan David Ortiz: One mystery remains