Oddly enough, the real culprits were Sunni Misunderstanders of Islam.
“20 Shiites pulled off buses in Pakistan, shot, killed: police,” from The Canadian Press, August 16 (thanks to Kenneth):
PESHAWAR, PAKISTAN””A Pakistani official says gunmen forced 20 Shiites off buses in northern Pakistan and killed them….
The official spoke on condition of anonymity because he was worried about retribution….
There have been several such sectarian attacks in the region in the past. Many Sunni extremists do not view Shiites as true Muslims.