Speculation is it might be an American…
Via IB Times:
Islamic State (Isis) commanders fighting in Libya are thought to have been targeted by a lone sniper, who has killed 3 high-level jihadis in just 10 days. As Daesh (IS) extremists gain ground in the war-torn north African country, a sharpshooter is said to be at work in the city of Sirte, systematically picking-off IS commanders one-by-one.
And, according to local media in the former Muammar Gaddaffi-stronghold, IS are now sweeping the city hunting for the marksman, dubbed on social media as the ‘Daesh hunter’. The coastal city has been overrun by the terror group, who now roam the streets freely.