An Iranian Revolutionary Guard officer, Colonel Mohammad Eskandari, was identified as the man that was beheaded in Syria last week. He was beheaded by the Al Qaida linked Al-Nusra Front Syrian opposition.
Iran and Hezbollah support Assad in the battle for control over Syria, while Al-Qaida and the US support the rebels/opposition/freedom fighters.
Iranian soldiers are actively involved in fighting in Syria for Assad.
And the US reportedly supplies the Syrian rebels, or at least the ones the US imagines are not linked to Al Qaida, with weapons and training to fight and overthrow Assad.
Meanwhile, the US is trying to woo Iran back into the US’s circle.