The Daily Mail reports that "[p]ublic executions, amputations, lashings and mock crucifixion have become a regular Friday fixture in jihadist-controlled areas of Syria, according to a UN human rights investigation." According to the article, the IS is forcing people--including children--to turn out to witness the executions. It also states that the bodies are placed on display for several days in order to terrorize the population.
Sounds like it is time for a counter-terror campaign against ISIS. I'm sure that enterprising Syrians--modern day Ḥashshāshīn, so to speak--could find ways to make ISIS fighters or leaders disappear one or two at time, with heads or other parts showing up at inopportune times and places.