The accounts of law enforcement’s actions during one of the worst school shootings in history are among a trove of recorded investigative interviews and body camera footage obtained by ProPublica, The Texas Tribune and FRONTLINE. Together, the hundreds of hours of audio and video offer a startling finding: The children in Uvalde were prepared, dutifully following what they had learned during active shooter drills, even as their friends and teachers were bleeding to death. Many of the officers, who had trained at least once during their careers for such a situation, were not.