The turbaned gunmen who infiltrated Nairobi’s Westgate mall arrived with a set of religious trivia questions: As terrified civilians hid in toilet stalls, behind mannequins, in ventilation shafts and underneath food court tables, the assailants began a high-stakes game of 20 Questions to separate Muslims from those they consider infidels.

Numerous survivors described how the attackers from al-Shabab, a Somali cell which recently joined al-Qaida, shot people who failed to provide the correct answers.

Rutvik Patel, 14, was in the aisles at Nakumatt, the mall’s supermarket that sells everything from plasma TVs to imported kiwis, when he heard the first explosion. “They started shooting continuously, and whoever died, died,” he said. “Then it became calm and they came up to people and began asking them some questions. If you knew the answer, they let you go,” he said. “They asked the name of the Prophet’s mom. They asked them to sing a religious verse.”

Survivors’ chilling accounts combined with internal al-Shabab documents discovered earlier this year by The Associated Press mark the final notch in a transformation within the global terror network, which began to rethink its approach after its setbacks in Iraq. Al-Qaida has since realized that the indiscriminate killing of Muslims is a strategic liability and hopes instead to create a schism between Muslims and everyone else, whom they consider “kuffar,” or apostates.

“What this shows is al-Qaida’s acknowledgment that the huge masses of Muslims they have killed is an enormous PR problem within the audience they are trying to reach,” said Daveed Gartenstein-Ross, director of the Center for the Study of Terrorist Radicalization. “This is a problem they had documented and noticed going back to at least Iraq. And now we see al-Qaida groups are really taking efforts to address it.”

The evolution of al-Shabab is reflected in a set of three documents believed to be written by the terrorist group and found by the AP in northern Mali earlier this year. They include the minutes of a conference of 85 Islamic scholars, held in December 2011 in Somalia, as well as a summary of fatwas they issued last year after acceptance into the al-Qaida fold.

Baptized with the name al-Shabab, meaning The Youth, in 2006, the group began as an extremist militia, fighting the government of Somalia. As early as 2009, it began courting al-Qaida, issuing recordings with titles like, “At Your Service Osama.”

Until the Westgate attack, the group made no effort to spare Muslim civilians, hitting packed restaurants, bus stations and a government building where hundreds of students were awaiting test results. And until his death in 2011, Osama bin Laden refused to allow Shabab into the al-Qaida network, according to letters retrieved from his safehouse in Pakistan. The letters show that the terror leader was increasingly troubled by regional jihadi operations killing Muslim civilians.

In an email exchange this week with The Associated Press, al-Shabab made its intentions clear: “The Mujahideen carried out a meticulous vetting process at the mall and have taken every possible precaution to separate the Muslims from the Kuffar before carrying out their attack.” However, even at Westgate, al-Shabab still killed Muslims, who were among the more than 60 civilians gunned down inside.

Al-Shabab’s attempts to identify Muslims are clear in the 16-page transcript from the conference of Islamic scholars held in the Somali town of Baidoa, an area known to be under Shabab control in 2011, according to Somalia specialist Kenneth Menkhaus, a political science professor at Davidson College in North Carolina. The scholars issued several fatwas defining exactly who was a Muslim and who was an apostate.

The document states it is halal, or lawful, to kill and rob those who commit crimes against Islam: “The French and the English are to be treated equally: Their blood and their money are halal wherever they may be. No Muslim in any part of the world may cooperate with them in any way. … It leads to apostasy and expulsion from Islam,” it says. Further on it adds: “Accordingly, Ethiopians, Kenyans, Ugandans and Burundians are just like the English and the French because they have invaded the Islamic country of Somalia.”

Former FBI supervisory special agent Ali Soufan, who investigated the bombing of the United States embassies in East Africa as well as the attack on the USS Cole, said that the gathering of dozens of religious scholars in an area under Shabab control harkens back to an al-Qaida conference in Afghanistan around 1997. That conference defined America as a target, Soufan said, leading to the bombing of American embassies in Kenya and Tanzania in 1998.

“You see something very similar here,” Soufan said. “It’s the same playbook.”

— Rukmini Callimachi, Associated Press