They suspect Black Widows. Awful.
The ranks of the Shahidkas are filled mainly with 15-19 year old women. According to journalist Julia Jusik many of the women have been sold by their parents to be used as shahidkas, others have been kidnapped or tricked. Another group come from wahhabist families and are pressured to become shahidkas by their family. Only one out of ten act out of conviction or want revenge or want to die. Many have been prepared to the suicide by way of narcotics and rapes (making them ineligible for marriage). Several have been pregnant at the time. Mainly they are given no training at all in preparation for the suicides as no weapon skill is needed to strap on the explosives. Many don't even blow themselves up, but are blown up by remote control.