An international rights group released a report Wednesday detailing horrific atrocities committed by the Islamic State group in its Libyan stronghold of Sirte, including instances of “crucifixions,” public beheadings and shooting a man to death for “insulting God.” Human Rights Watch interviewed 45 residents in the coastal city who recounted “scenes of horror” since the extremist group, also known as ISIS, overran the area in February 2015.