An American forensics team is assisting Kenyan investigators in trying to figure out how the terrorists pulled off the deadly mall attack.
A Kenyan newspaper is reporting the perpetrators spent months studying the building. They even operated a store inside the mall where they may have stashed weapons.
More than 1,000 people survived the attack. Some are sharing their survival stories, including a 19-year-old who hid under suitcases for four hours.
Dorcas Mwangi said her brother texted her saying the terrorists were killing non-Muslims. He then sent her the words to an Islamic prayer.
"I was able to memorize it in case they found me," Mwangi told reporters.
Another survivor recounted his story to reporters.
"He asked if I was a Muslim? I said 'I am.' And he asked, 'Is this your woman?' I said, 'Yes, yes she is.' And then he said, 'Ask her to cover up' and then he pointed gun and said 'Leave.'"
Kenyan citizens are now observing three days of mourning for those killed in the attack.