He waited for his brother-in-law to cross the front line smuggling documents stolen from the Syrian dictatorship’s archives.

Detection could mean dismemberment or death, but they were committed to exposing the industrial-scale violence being used to keep President Bashar Assad in power.

Ussama Uthman, now 59, was building a vast record of the brutality — the first solid proof that Assad’s government was engaging in systematic torture and extrajudicial killings.

Now, safely in exile in France and with Assad having fallen in a surprise rebel offensive last year, Uthman is sharing how he, his wife and her brother teamed up to smuggle evidence of the horrific crimes out from under Syria’s infamous surveillance apparatus as war tore the country apart.

The photos of broken bodies and torture sites — records that were apparently kept to show higher-ups that underlings were following orders — suddenly began appearing online in 2014.

They spurred U.S. sanctions, and are being used to prosecute suspected war criminals and help Syrians find out what happened to family members who disappeared during the dictatorship.

During a recent interview in northern France — The Associated Press agreed to withhold the exact location due to security reasons — the only time Uthman's voice broke was when he recounted sending an elderly woman photos of a brutalized body and asking if she recognized her son.

“I send her five snapshots of her son’s body, torn under Bashar al-Assad’s whips, and she rejoices. She says, ‘Thank God, I have confirmed that he is dead," he recalled, shaking his head. “This sadness should have kept our flags at half-staff in Syria for years.”

With the Arab Spring sweeping through the Middle East in 2011, protests in the city of Daraa soon inspired demonstrations throughout Syria.

The government responded with force, but rather than cow the populace, the brutality sparked a civil war that pitted rag-tag groups against the armor and air power of the military and Assad's allies.

When news broke that first year of a massacre in Hama, Uthman, a construction engineer from the Damascus suburb of al-Tall, swore he'd help topple Assad.

He didn’t know how until he got a call from his wife’s brother Farid al-Mazhan, a military police officer who asked him to meet in person — electronic communications were too risky.

Al-Mazhan showed Uthman gory photographs taken by the military’s forensic pathology department, and he could access more inside large databases of photos of Syrians who had been brutalized.

The two launched a secret operation that would eventually smuggle more than 53,000 photographs out of Syria showing clear evidence of rampant torture, disease and starvation in the country's lockups.

The operation was incredibly dangerous but straightforward.

Because of his military role, al-Mazhan was able to enter rebel-held areas, where he would secretly pass CDs, hard drives and USB sticks containing photos and other documents to Uthman or his wife, al-Mazhan's sister Khawla al-Mazhan.

The team eventually expanded to seven, with Khawla serving as the “mortar of th meosaic," said Uthman. It was she who first suggested using the photos to try to topple Assad.

“Why don’t we use these images to bring down the regime?” he recalled her saying.

Uthman adopted the nom de guerre Sami. Farid al-Mazhan took Caesar, the name their operation would become known as: the Caesar Files.

Deciding to escape Syria — an estimated 6 million people fled during the war — the team uploaded 55 gigabytes of photos and documents to a foreign server that had been taken or created between May 2011 and August 2014.

They then began furtively moving their extended families to neighboring countries. Diplomats eventually helped Uthman’s family settle in France in 2014.

Once safely out of Syria, they began publishing the materials, sparking immediate and widespread condemnation of Assad.

As families scoured the ghastly archive for signs of what happened to their loved ones, the team gave copies to European prosecutors.

Authorities in France, Germany, Belgium, the Netherlands and Switzerland have arrested or initiated legal proceedings against former Syrian officials accused of torture and killings.

Hoping to plug the leak, Syrian authorities tightened their grip on their archive. Gradually, though, the team reorganized into cells to limit their exposure and grew to roughly 60 members both inside and outside of Syria. They built a second tranche of evidence, the Atlas Files, from 2014 until 2024.

Late last year, as they were starting to organize this colossal yet-unreleased catalog of cruelty — it's nearly three times the size of the first — startling news broke: Rebels had seized Syria’s second-biggest city, Aleppo.

Assad's downfall was stunning. Within 10 days, rebel forces sprinted across government-held territory to take Damascus, forcing Assad to flee to Russia and ending his family's nearly 54-year rule.

The sudden power vacuum bred chaos, with rebels flinging open the doors of the country's most feared prisons to the utter surprise of the wretched souls inside.

Team members still in Syria and families of the missing rushed to the sites in search of new information — more than 130,000 Syrians disappeared during the war, according to the International Commission of Missing Persons.

Uthman says so much evidence was lost in the immediate aftermath of Assad's ouster that it was akin to the new authorities “destroying evidence, tampering with the crime scene.”

Documents lay scattered on rainy streets, psychologically shattered prisoners wandered out of broken jails, and wild dogs chewed on bones in mass graves, he said.

With al-Sharaa set to visit Washington on Monday, partly in the hopes of lifting sanctions against Syria, his government claims it is doing all it can to reckon with the crimes committed under Assad.

During a news conference Wednesday in Damascus, Reda al-Jalakhi, who heads the government's National Commission for the Missing, acknowledged that “in the first two days of the liberation, there was some chaos and a lot of documents were lost.”

But he said the new authorities quickly took control of Assad's old lockups and is preserving the remaining documents and evidence.

He thanked the Caesar Files team for providing some documentation to the commission, but he didn't signal any plans for ongoing cooperation, saying the government would build a centralized database to find the missing.

With a defiant twinkle in his eyes, Uthman said his team's work will continue as fresh sectarian violence bloodies the country. Like many Syrians, they dream that one day, Assad could stand trial in Damascus.

That would require ironclad evidence.

AP video by Mark Carlson

Production by Sam McNeil