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.
A State Department spokeswoman said Sunday there were five Americans among the injured, but none among the dead.
"Obviously it's an enormous offense against everybody's sense of right and wrong," said Secretary of State John Kerry. "It represents the seriousness and the breadth of the challenge we face with ruthless and completely reckless terrorists, and we're going to pursue them."
The U.S. Embassy asked personnel to stay in place Sunday and avoid the Westgate Mall area and any large gatherings. All U.S. citizens in Kenya were urged to register online so the embassy can provide them with updated information on travel and security -- and can contact them in case of emergency.
Israel's Foreign Ministry said one national was slightly wounded and three escaped. A cafe at the mall is owned by an Israeli, but the ministry does not believe the mall was targeted because of that.
The Ghana president's office said literary figure Kofi Awoonor was among those killed in the attack.
"Such a sad twist of fate to place Prof at the wrong place at the wrong time," President John Mahama said in a statement.