"It would be very unusual for a woman to be involved in one of these operations," he said. "Typically these groups are misogynist. Their view is the woman should be in a home and shrouded in a body veil."
Lewthwaite's husband, Germaine Lindsey, was one of the suicide bombers killed in the 2005 attack on London's transportation system. His Buckinghamshire-born widow is wanted by Kenyan authorities for her alleged role as an Al-Shabaab and al Qaeda-linked financier.
A day of horror
The calm was shattered around noon local time Saturday. Gunshots erupted as shoppers picked up groceries, savored lunch and browsed through the racks at stores.
Before long, pools of blood smeared pristine hallways. Bodies lay strewn across the floor.
Uche Kaigwa-Okoye was sipping coffee when he heard what first sounded like a fallen table, then the continuing rat-a-tat of gunfire. As the gunshots became louder, screaming crowds headed for the exits.
He joined 20 people who took shelter for about five hours in a women's bathroom cubicle.
"They had grenades, and it was really, really loud," he said of the attackers. He noticed tear gas in the hallways as well.
"All of us felt like they were close," he said.
As people texted family and friends outside the mall, word spread that nobody could be trusted. And even if the good guys could be sorted from the bad guys, the intermittent barrages of gunfire made any escape attempt seem futile.
Sara Head, a Washington resident, experienced similar horror in the mall's parking garage. As her car pulled up, she heard gunfire. She crawled underneath and hid behind cars before getting into a stairwell.
Eventually, the stairwell lights came back on and the door to a nearby supermarket opened. She dashed through, passed a nearby loading dock and fled to safety.
"There was blood throughout the supermarket," Head said. "It wasn't clear if it was OK to exit."
Several Kenyan agencies made a plea for blood donations.
"Hospitals are appealing for more blood, the response is incredible but more is needed," tweeted Francis Kimemia, secretary to the Cabinet.
Foreigners among casualties
Most of the casualties are Kenyan, authorities said. But the mall is popular with expatriates and foreign nationals, who were among those killed and injured.
Those killed include three British citizens, two French nationals and two Canadians, including a diplomat, their governments said.
Several American citizens were among the wounded, including Elaine Dang, a University of California, Berkeley, graduate.
Dang worked as the general manager for Eat Out Kenya, which confirmed her injuries on its Twitter and Facebook pages.