Medical and security sources in the Libyan city of Benghazi say unidentified gunmen shot dead an American teacher working at an international school as he was jogging Thursday.
Ronnie Smith, a 33-year-old U.S. citizen from Texas, had been teaching chemistry for about 18 months at the International School Benghazi - a Libyan-owned institute that follows an American curriculum, a school official told local media.
No one has yet claimed responsibility for the killing, but suspicion is likely to fall on Islamist militants active in the city.
The U.S. State Department confirmed Smith's death and said it is contact with his family.
Smith's killing triggered an outpouring of emotion on social media networks.
The Libyan Youth Movement tweeted, "It is with a very heavy heart that we announce the death of Ronnie Smith... shot & killed in #Benghazi."
International School Benghazi is one of the few foreign schools still operating in Libya, with most of them having shut down in the last year because of the growing insecurity.
Libya's heavily armed militias, with roots in the 2011 war against dictator Moammar Gadhafi, have proliferated since his overthrow and have worked against successive transitional governments and parliament.
In late 2012, Islamist militants assaulted the U.S. consulate in Benghazi, killing the U.S. ambassador to Libya.