Shiite killing Sunni.
Sunni killing Shiite.
Both killing infidels.
Never ends.
Countries like Yemen are nearly 100% Muslim so they no longer have infidels to kill as a result they go after the heretics. It is important to understand that even a small doctrinal difference can make one a heretic and worthy of death. Think of the People’s Front of Judea and the Judean People’s Front.