who kills?

In the Reuters article, Iraqi Army Seeks to Control Tal Afar, 200 Dead, Nameer Nouredeen quotes Abdelaziz Jasim, the defense ministry official supposedly in charge of operations at Tal Afar:

"Overall 157 terrorists have been killed and 291 arrested since the beginning of the operations," he told a news briefing in Baghdad before the new offensive in Tal Afar.

How do they know these people are "terrorists?" It sounds like the Vietnam body count logic of, "We only kill terrorists, so therefore, anyone we have killed must be a terrorist."