BEIRUT (AP) — For years, the Siyam family have hoped to one day be reunited with their son Wassim, whom they believe is being held in a Syrian government prison after disappearing at a checkpoint nearly a decade ago. That hope was dashed the moment they saw him in a newly leaked video: He was one of dozens of blindfolded and bound men shot dead by Syrian security agents one by one and thrown into the trenches. “It shocked our hearts,” Siham Siyam said of the horrific video, which was filmed in 2013 and appeared late last month. “They killed...