The soldier captured more than just a basic selfie. A few seconds after he starts filming himself the vehicle behind him trips an IEDs pressure plate.
Two soldiers in the vehicle were killed and a third seriously wounded after the blast hit the vehicle. It is very likely the IED was planted by ISIS as the attack took place in Deir Ezzor. Muraselon.com indicates that the IED was probably planted a “long while ago,” which indicate that it was triggered by a pressure plate, rather than detonated by a nearby trigger man.