Al-Shabab forces killed at least 36 non-Muslim people at a Kenyan quarry in an attack early Tuesday morning. The Somali Muslim extremist group specifically filtered out non-Muslims from the workers at the quarry in the northern Kenyan city of Mandera and shot them dead. Witnesses said some victims were ambushed in the tents they were sleeping in near the quarry. Four were beheaded and the rest were lined up and shot in the head at close range, according to a driver who visited the scene. Al-Shabab killed 28 Kenyans in an attack specifically targeting non-Muslims in the same region last week. On Monday night, hours before the attack, a man was killed at a bar in a nearby district that is popular with non-Muslims. Al-Shabab has stepped up its attacks on Kenya since 2011, after Kenya started sending troops to its border to fight terrorist forces. It was responsible for last year’s horrific attack on a Nairobi mall that resulted in at least 67 deaths.