Thirty Seconds on the Gymnasium Floor

Marcus DeLeon was seventeen years old when his heart stopped during the third quarter of a Friday night basketball game in Waco, Texas. He crumpled at the free-throw line like a marionette whose strings had been cut. The crowd went silent. Then the screaming started. Coach Rivera didn't hesitate. She sprinted to the wall, yanked a white plastic box off its mount — an automated defibrillator most people walked past every day without a second glance — and knelt beside Marcus on the hardwood.…