both the shooters are Turekys

BBC speaking Turkish, a Turkish businessman living in Utrecht, Gökmen Tanis 2 July 1981 Yozgat was born, previously went to Chechnya and said that he fought.

"A few years ago he was arrested and released for his connection to ISIS. He did not interfere with the Turkish society, it was a reclusive one." said.

https://www.bbc.com/turkce/haberler-dunya-47611776

both fromk/been Turkey