Police only thought Jos Brech was curious when he rode his bicycle past an active crime scene in a forest in the Netherlands in August 1998.

The officers had just recovered the body of 11-year-old Nicky Verstappen, who, on a summer camp trip, had disappeared from his tent the night before. The boy had been raped and killed, police said, in a case that would haunt the nation in the decades to come.

But, that night, Brech said he didn't know anything. Police took his name and let him go.

They kept his name for a long time — until finally, this year, it came up again.

In October 2017, authorities in the Netherlands launched a massive DNA investigation ahead of the 20th anniversary of Verstappen's death, seeking DNA samples from more than 20,000 men, including Brech, that they would compare to DNA left behind at the crime scene. If police got lucky, they could identify the alleged killer's family members through partial matches. It was the largest such DNA kinship investigation in the country's history, Dutch broadcaster NOS reported, and more than 14,000 men agreed to voluntarily offer up their genetic information to help police.

But one man was conspicuously not among them.

Brech, in fact, had disappeared the same month the testing began.

Police had grown increasingly suspicious of Brech after his family reported him missing in April, the NL Times reported. He had left on a hiking trip through the Vosges Mountains in France in October 2017, and told his family he would comply with the DNA request once he returned.

He didn't come back. But authorities still found a way to seize his DNA anyway.

Brech was arrested Monday on charges of murder and grievous bodily injury after two of his relatives' DNA turned up in the massive screening and after his own DNA, taken from his cabin in the Vosges Mountains, turned out to be a match, according to Dutch police. Police compared his DNA sample to that found on Verstappen's pajamas in 1998, leading them last week to publicly identify Brech as the suspect in Verstappen's killing.

The announcement kicked off an international manhunt for the 55-year-old Brech, who according to Europol spent much of his time teaching wilderness survival skills called "bush crafting." He was apprehended in Spain on Monday, where police believe he had gone into hiding once the DNA investigation began. Spanish police found him on his way to chop wood in the mountains, they said Monday.

A witness had tipped off police after recognizing his picture from police and media reports, police said. He earned a spot on Europe's Most Wanted Fugitive List. He is awaiting extradition and has not filed a plea in the case.

Officials were so pleased with the DNA investigation that some are considering the possibility that the familial DNA testing be mandatory rather than voluntary, Minister of Justice and Security Ferdinand Grapperhaus told Dutch media.

"I think it is really important that we realize that we have technological developments in society that can ease the pain of relatives," Grapperhaus said, NL Times reported.

The Netherlands has used the technique multiple times in the past to nab suspects accused in violent, unsolved crimes, though never to this degree.

In December, police arrested a man suspected of raping and killing a woman in 1992 after testing the DNA of 126 men, one of whom was identified as a family member of the suspected killer, Dutch News reported. In 2012, a mass DNA test of nearly 6,600 men led to the arrest of a farmer suspected in the rape and killing of a 16-year-old girl.

Use of so-called DNA dragnets in the United States is rare. Police in Oklahoma City have taken blood samples from more than 200 men to test it against evidence found inside the car where a college student was raped and killed in 1996, CBS News reported. The men voluntarily gave samples. Some who refused were served with search warrants, the outlet reported.

In 2003, police in Louisiana asked 800 men to submit blood samples in search of a serial killer, allegedly threatening some men by telling them if they didn't participate, the newspapers would find out they weren't being cooperative, the New York Times reported then.

And in 2005 police in the small town of Truro, Mass., wanted the entire adult male population — 790 men — to submit their DNA to try to solve a three-year-old murder, evoking outrage from the ACLU.

"They're not very effective and they're certainly not voluntary," a spokesman for the ACLU said of the tests in an interview with the New York Times. "It's either give a sample or you're a suspect. It turns the classic American concept of 'innocent until proven guilty' on its head."