The news that the ISIS militant who beheaded photojournalist James Foley appeared to have a British accent came as no surprise to Dimitri Bontinck — a Belgian man who carried out a daring mission to lure his jihadist son out of Syria and who has helped three other dads do the same.
In an interview with NBC News' Richard Engel on Wednesday, as he tried to arrange another rescue, Bontinck estimated that ISIS has 5,000 to 6,000 Europeans in its ranks, and another 10,000 to 15,000 from other Middle Eastern countries.
Despite the group's brutal tactics, most of its foreign fighters are true believers who have no interest in abandoning the cause and coming back to the West. "Ninety-eight percent stay," he said. "It's only two percent who will change their mind and return home."
Last year, Bontinck left his home in Antwerp and traveled to one of the most dangerous regions in Syria to find his 18-year-old son Jejoen, whom he described as an idealist who joined a precursor to ISIS because he wanted to help fellow Muslims battling the regime of Syrian President Bashar al-Assad.
"It was the only solution — action! I couldn't stay home," he said.
He was briefly taken hostage, but eventually located Jejoen and convinced him to come home. "We never use force," he said.
Since then, Bontinck said he has led three other fathers on similar successful missions. When NBC spoke to him, he had just crossed over into Turkey from Syria, where he was trying to help another family connect with their son.
He said his work has given him a window into how ISIS recruits foreign fighters, their anger at the West for not doing more to protect Syria against Assad, and the rumblings that the beheading of Foley is only the beginning of attacks targeting the West.
"I think the world is in danger from this group," he said.