Al-Mousa, a 23-year-old editor for Raqqa is Being Slaughtered Silently (RBSS) was shot dead in Idlib province, according to news reports and RBSS, the Syrian citizen journalist group CPJ honored with its 2015 International Press Freedom Award.
Abdel Aziz al-Hamza, a spokesperson for RBSS, told CPJ that al-Mousa was shot twice in the head in front of the family home in Abu al-Duhur, a town in Idlib, by a masked attacker on a motorcycle. In a picture CPJ has viewed of al-Mousa's body, which his family sent to al-Hamza, bandages can be seen around the journalist's head and neck.
Al-Mousa's murder came amid a campaign of violence by the Islamic State militant group against members of RBSS and other Syrian journalists. Islamic State claimed responsibility for the murders of at least two RBSS members. In October 2015, Ibrahim Abd al-Qader was killed alongside fellow journalist Fares Hamadi in Urfa, southeastern Turkey. In May 2014, Al-Moutaz Bellah Ibrahim was kidnapped and murdered by the militants.
Some supporters of Islamic State claimed on Twitter after al-Mousa's murder that their "soldiers" killed him, and referred to him as an "apostate" and "agent of crusaders." In a video published online on March 8, 2016 by Islamic State's local branch in Deir Ezzor, Syria, the militant group claimed responsibility for the murders of all four journalists. The video, "Escaping won't do you any good," shows two new hostages who identify themselves as Mohamed al-Kardoush and Jamal al-Ati, whom the militants accuse of providing information to Western governments. It was not immediately clear if the hostages are journalists.
Al-Mousa was also named in a video released by Islamic State on January 3, 2016 showing the murder of five men. In the 10-minute video the men say they covertly filmed Islamic State activity and opened an Internet café to share material with news outlets and Turkey-based activists, including al-Mousa. Al-Hamza denied any of the hostages worked with RBSS. Western intelligence agencies are investigating the authenticity of the video, according to news reports.
The Nusra Front, an al-Qaeda affiliate that controls Idlib, told al-Hamza it is investigating al-Mousa's death.
According to al-Hamza, al-Mousa edited and vetted reports for RBSS from Raqqa out of Gaziantep in Turkey and Idlib in Syria. He went into hiding in Idlib several months before his death, after Islamic State kidnapped his father and released a video of his murder in August 2015. One week after al-Mousa's murder, Islamic State claimed to have killed the journalist's aunt, Maria Hasan al-Shams, al-Hamza said. She was taken captive in October after militants found a picture on her phone of Hamoud al-Mousa, who is the brother of the dead journalist and one of RBSS's co-founders, al-Hamza told CPJ.
Since April 2014, RBSS has documented the abuses of Islamic State in Raqqa. RBSS, which has been declared an "enemy of God" by the militants, also reports critically on the Assad government's bombings, other rebel forces, and civilian casualties caused by airstrikes.