For years, Khadija Adam had gone to Nairobi’s Westgate shopping mall on Saturdays. She had her hair styled at the Ashley Salon, attended to her mobile-phone at Safaricom, shopped at the Nakumatt supermarket. Sometimes she stopped into the Millionaires Casino. Adam, a former model and a warm, boisterous talker, knew many shop owners by their first names, and always bumped into friends. Often, she would get caught up for hours in conversation—she speaks Swahili, Somali, English, and some Arabic—at ArtCaffe. Like many in Kenya, Adam is part Kenyan and part Somali, and a Muslim. “You know how Somalis are,” she told me, “we always have to get the story on everything.”

Adam arrived at Westgate a few minutes after noon last Saturday. She parked on an upper terrace in the building’s rear. Nearby, around some tents, a crowd of children and their parents were assembled for a junior-chef cooking contest. One of the mothers invited Adam over. She said that she would come back after her salon appointment. She walked into the mall, whose interior is shaped like a “d,” with stores and restaurants surrounding a central atrium. She went into the Safaricom store.

“Then I heard the sound,” she said. “PAH! There were three shots.”

Adam works at a mining company in Garissa, a city in northeast Kenya, near the border with Somalia. In the last few years, Garissa has become used to bombings, shootings, and kidnappings—most of them blamed on the Shabaab, the Somali Islamist insurgent group. She knows the sound of gunfire. But this was different. “I’ve never ever heard such gunshots,” she said. “These guns were amazing.”

Adam rushed to the entrance of the store. She saw a Kenyan policeman crouching by a pillar, aiming across the atrium. There was another deafening volley and bullets tore into the policeman: “The pillar was literally looking like it was on fire.” Then running and screaming. She backed into Safaricom.

At Ashley Salon, a level above, where Adam had had a 12:30 appointment, Simon Kinyanjui, a stylist, was washing a woman’s hair when he heard the gunfire. “We thought maybe the water-heater had blasted,” he told me. Kinyanjui and a coworker left the salon and peered into the atrium, where they saw police with their guns drawn. “That’s when they were rained with bullets,” Kinyanjui said. They ran back into the salon. Kinyanjui told the customers inside to hide. One got under a massage table. Others crammed into the bathroom. He locked the door and turned off the lights.

Two other stylists, Godfrey Njoroge and Thomas Kamau, were on the other side of the atrium, on a smoking patio beside the Java House restaurant, facing onto the rear terrace. Njoroge was putting out his Sportman cigarette when “massive, massive gunshots” rang out from the far side of the tents. Kamau ran to the other end of the lot and looked over a low wall. Below him, he saw two men with rifles and what appeared to be ammunition draped over their shoulders. Black cloths were wrapped around their heads. One was shooting at a security guard, the other toward the mall. One of the men looked up at Kamau and raised a hand in the air.

“He screams ‘We are al-Shabaab!’” Kamau told me. “When he said that I repeated to the guys behind me, ‘Did they say al-Shabaab?’”

Kamau decided not to wait for confirmation. He and Njoroge moved toward the Java House, along with the frantic children and parents from the cooking contest. Just then, gunfire from inside the mall emptied the restaurant. “People were running with cups of coffee still in their hands, spilling it all over the floor,” Njoroge said. “People were screaming. Bangs inside, bangs outside.”

The two groups collided on the terrace. Kamau suggested that they try to climb down a wall facing onto a residential area behind the Westgate. Njoroge didn’t like this idea. “I’m going back inside,” he said, and dashed into the Java House.

When Khadija Adam had walked onto the escalator, at about 12:15, she’d looked down and seen Janet Mulonzia at her usual place behind the counter of the African Lady leather-goods kiosk, on Westgate’s ground floor, near the main entrance. Mulonzia and her coworker, Rosa, were attending to an order of handbags.

When shooting broke out in front of the main entrance, Mulonzia’s immediate thought was a robbery. A large Barclays bank branch was near the entrance. If a robbery ever did occur, Mulonzia had thought in the past, the safest place to hide might be in the cupboard below the kiosk counter. So, without much debate, she and Rosa kneeled down and crawled in. They listened as the gunfire increased and then became constant. Mulonzia could hear firing and screams coming from ArtCaffe, too, on the other side of the kiosk from the entrance.

After the running and screaming died down, she heard people speaking in a language she didn’t recognize, accompanied by deliberate, slower footsteps. Through the gap between the bottom of the cupboard doors and the floor, she could see feet. She heard loud whistles, perhaps signals, and then people conferring in Swahili, the common language of Kenya. Next to African Lady is a beauty shop. “Someone, I think maybe one of the gangsters, was yelling at the people in the beauty shop to open the doors,” she said. They yelled in Swahili, “We can get in there and you can make our faces!”

Upstairs, at Safaricom, Khadija Adam heard yells from the atrium. “When I heard the words ‘Allahu Akbar!’ and the gunfire, I knew we were in trouble,” she said.

Adam and the others—she estimates that there were more than forty of them in the store—piled into a back room. Among them were several white people. “If they come in and they see white people, they won’t care, they’ll kill all of us,” she said. There was a small cubicle with the store’s surveillance-camera monitors in it. She told the white customers to go in it and hide, and reminded everyone to turn off their cell phones or put them on silent mode. “As we were sitting there, you could hear everything.” Between bursts of gunfire and explosions, she heard what sounded like people moving around in air ducts. She wanted to call out to them. But a man who identified himself as U.N. security personnel said it could be the assailants. So they waited, in silence. They passed around cups of water and held each other’s hands.

Adam’s husband, in Hong Kong, texted her. “He said ‘These are terrorists, and they’re killing anybody who’s non-Muslim. Tell all the foreigners with you not to go out,’” she said. “I started crying at that point, when I realized it was al-Shabaab. I suspected before, but you know you self-doubt. When I heard it on a text coming from Hong Kong, then I know it’s in black and white.”

In the drafts folder on her phone, she saved a series of texts—to her husband, relatives, friends—in case the attackers got into the store. “I was waiting for the last minute to press send.”

One level above, in the salon, Simon Kinyanjui quietly climbed up a ladder to a loft area, which had a television and a sofa, where he and his coworkers normally relaxed between appointments. Now they sat looking at each other and their phones, listening as the gunfire approached and explosions rattled the building. On the wall was a vent with adjustable blinds. Kinyanjui slowly opened them and peered out. He saw three people, dressed in black and camouflage, carrying rifles, approach the salon. One pulled on the door. Finding it locked, the group moved on to a neighboring store, Planet Media, and began shooting at its display windows. The person who appeared to be the leader of the three, who also carried a pair of knives on a belt, had what looked to Kinyanjui to be long hair—like a woman’s. (Reports that a woman, possibly a Caucasian woman, was among the attackers, have not been confirmed.) Kinyanjui texted his coworkers who weren’t in the shop. He found most of them. But not Godfrey Njoroge.