Protesters in Syria held a sit-in Wednesday demanding justice for four activists who were forcibly disappeared in 2013 and whose fate remains one of the most haunting mysteries of the country's 13-year civil war.

On Dec. 9, 2013, gunmen stormed the Violation Documentation Center in Douma, northeast of Damascus, and took Razan Zaitouneh, her husband Wael Hamadeh, Samira Khalil and Nazem Hammadi.