The suspect looked back quickly. Then he ducked into the mass of people who were walking to the train entrance at Fifth Street. Using rush hour commuters and wide-eyed tourists as human shields, he waded into the crowd, stuffed his jacket into a trash can, and popped out the other side as Sandy sprinted to catch up.

“Stop now!” she shouted, as two other officers fell in behind her.

Knowing that the police couldn’t shoot into the crowd, the suspect bolted down Market Street, weaving through throngs of tourists who’d come to see the Liberty Bell and Independence Hall.

He ran while the sound of sirens filled the air, his fists pumping and his legs churning as adrenaline made him move faster than Sandy and every cop who joined the chase.

Sandy knew that he could hear the heavy footfalls of the pursuing officers. She knew that he could hear the radio chatter that betrayed his location. She knew that he was desperate.

As she watched him dodge in and out of the crowd of commuters and tourists, she knew something else, as well. If they didn’t catch him soon, an innocent bystander would be hurt.

With sweat streaming down her face and cramps locking up her muscles, Sandy ran harder, even as her lungs were ablaze and her breath came in heavy gasps.

With rush hour traffic clogging streets too small for heavy volume, and commuters flocking to subway platforms and bus stops, she caught sight of the suspect once more. As she and other officers closed in, the suspect took advantage of the chaos around him.

Stepping into the midst of the crowd at Ninth and Market, he threw his head back. “They’re shootin’!” he shouted as loud as he could.

At that, the people around him ran in every direction. As they did so, he moved toward a flight of steps leading to the Gallery shopping mall. Sandy saw him at the last moment, just as he disappeared down the steps and through the mall’s rotating glass doors.

To the suspect’s right were kiosks and a sandwich shop, a bookstore, and a dimly lit passage to the Market-Frankford Elevated’s Eighth Street stop. To his left was the passageway that would lead past the food court and toward the Twelfth Street exit.

“There he is!” Sandy shouted as she ran through the doors behind him.

The suspect ran to his left, knocking down an old woman with a two-wheeled shopping cart and jostling a young boy whose heavy book bag nearly tipped him over. He smashed into a kiosk filled with cell phones, sending the glass display tumbling to the red brick floor.

Shards of shattered glass popped up toward his face, and one of them opened a gash near his eye. Still, he kept running, even as police officers came toward him from the escalator at Tenth Street.