Militants riding a motorcycle shot the man in his car in the southern city of Taiz on Sunday. Yemeni officials say the American had been working at a European-run language institute. Authorities launched an investigation to find the perpetrators of the attack.
A U.S. State Department official confirmed the killing of the U.S. citizen in a statement sent to VOA, condemning it as a "heinous crime" and urging Yemen to bring those responsible to justice.
Al-Qaida linked group Ansar al-Sharia sent a text message to Yemen-based journalists saying it killed the American because he was a Christian missionary. Islamist militants often accuse Western aid and development groups of proselytizing.
A Swiss woman working as a language teacher in Yemen's western port of Hodeida was abducted last week. The identity of the kidnappers remains unclear.
Al-Qaida's Yemeni affiliate is active in Yemen's center and south, where its fighters seized several towns in Abyan province last year.