A man who murdered 39 people at an Istanbul nightclub suspected to be the ISIS killer, AP reported quoting Turkish mass media.

Captain Abdullah Ağar, a terrorist expert who analysed footage of the attack taken by security cameras, described the suspect as “highly trained”.
“He is stable, practical, knowing how to get the required result, cold-blooded and expert”, he told Turkish media.

The attack on night club of Reina in Istanbul occurred on New Year's Eve. The terrorist armed with submachine gun shot the police officer protecting club, rushed into the room with more than 700 people and opened fire at them.
According to the Ministry of Internal Affairs of Turkey, 39 people were killed, 69 wounded.
An investigation is underway.