An Iraqi old man on Sunday shot dead seven Islamic State (IS) militants in revenge for the killing of his son by the extremists in Iraq's northern central province of Salahudin, a provincial security source said. The incident took place in the morning when Basil Ramadan, in his 60s, opened fire from his AK-47 assault rifle on a group of IS militants at a checkpoint in the provincial capital city of Tikrit, and killed seven of them before they shot him dead, the source told Xinhua on condition of anonymity.