It was Waddah al-Hitari’s beard that killed him. Militiamen on the streets of Yemen’s capital shot him dead one Friday because he looked like a terrorist, colleagues of the young doctor said.

Hitari was killed by a member of the Houthis, an armed Shi’ite faction whose fighters had swept down from the north and stunningly captured Sanaa from the army about a month earlier.

Their arrival following anti-government protests threatens to further destabilize Yemen, already wracked by political turmoil since the Arab Spring revolutions of 2011. […]