Syrian documentary filmmaker and anti-ISIS activist Naji Jerf was assassinated in the Turkish city of Gaziantep yesterday. His own organization, “Raqqa is Being Slaughtered Silently,” announced the news of his murder on Twitter. In the statement the group says Jerf was gunned down by an unknown assailant using a silencer-equipped pistol.

Jerf was killed shortly after he and his family were granted a visa for asylum in France. They were set to depart for Paris later this week, a friend says.

Jerf was a true modern hero. Having escaped from Syria, he might have built a new life for himself in Turkey or elsewhere, but the father of two chose to make documentaries exposing ISIS’ many crimes against humanity in Raqqa, the Syrian city the group considers the capital of its radical Islamic caliphate. That put him on the hit list.

According to Turkish media, Jerf was producing a new documentary on massacres carried out by ISIS jihadists when he was assassinated. The website T24 news reports that Jerf was “hit by a bullet in the head as he was walking in the street.” He was transported to the hospital, where he died.

Jerf is the third Syrian anti-ISIS activist to be murdered while hiding in Turkey. Earlier this year, Ibrahim Abdelkader and a friend were found decapitated in a house in the city of Sanliurfa. Like Jerf, Abdelkader worked for “Raqqa is Being Slaughtered Silently.” He, too, was a known target of ISIS’ assassins.

The murder of Jerf should increase the pressure on Turkey to crackdown on ISIS’ presence in its cities. I visited Gaziantep myself earlier this month and saw many Syrians on the streets; some of them were women and children, but the majority seemed to be young men. It doesn’t take a genius to figure out that at least some of them may share ISIS’ radical Islamic ideology and should therefore be monitored by Turkey’s intelligence agency, the MIT.

What’s more, even if it’s difficult to keep track of all these young men — there are approximately two million Syrian refugees in Turkey right now — it certainly is possible to protect the few prominent activists, such as those working with “Raqqa is Being Slaughtered Silently.” It says a lot about Turkey, and none of it good, that it doesn’t seem willing or able to do so.