The incident occurred in a northern Iraqi village in November 2016 when an SAS team was tracking ISIS operatives in areas controlled by the group.
The terrorists had stopped a group of civilians made mostly of women and children from escaping the village and were preparing to fire at them with a machine gun from a nearby building. The SAS team made the decision to open fire and save the civilians.
Using a .338 Lapua Magnum, the sniper took aim and fired at the first terrorist, striking him in the head. The bullet went through the man's skull and struck the other terrorist standing behind him, killing them both instantly. The bullet then ricocheted off a wall and fatally struck the third terrorist in the neck.
The shot was made from a distance of over one mile at 1,800 meters.
This is not the first instance in which the SAS has maximized the bullet-to-kill ratio on ISIS. According to British media, in 2015 a similar case occurred in which an SAS sniper shot a terrorist in the chest, which set off an explosive vest he was wearing and killed two additional terrorists standing near him.