The two masked killers burst through a door and, without saying a word, swept the conference room with semiautomatic rifle fire, spraying more than 100 rounds before they fled, just two or three minutes later.

A new report chronicles in vivid detail the Dec. 2 terrorist attack in San Bernardino, Calif., where Syed Rizwan Farook and his wife, Tashfeen Malik, killed 14 people and wounded 24 others. The couple pledged allegiance to the Islamic State, committed the rampage and died hours later in a wild shootout with the police, when Mr. Farook was shot 25 times and Ms. Malik was hit 13 times.

The report contains the first official account of how the killers were identified and tracked down, with a handful of officers playing crucial roles. And it reveals a wealth of specifics that had not been made public before, including the number of gunshots, and the horrors that officers and victims encountered.

The scene that police officers found minutes after the massacre overwhelmed the senses: dozens of maimed or dead bodies, spattered and pooling blood, the haze and smell of gunfire, a shattered pipe pouring water from the ceiling, a wailing alarm. And wounded victims pleading for help, clutching at officers whose first priority was to find the attackers.

“It was the worst thing imaginable — some people were quiet, hiding, others were screaming or dying, grabbing at your legs because they wanted us to get them out, but our job at the moment was to keep going,” the patrol officer said. “That was the hardest part, stepping over them.”

Making Decisions on the Fly

The report was produced by the Police Foundation, a policy study group in Washington, with help from the Justice Department and local law enforcement agencies; the authors interviewed more than 200 people, from police chiefs to survivors.

After The New York Times obtained a draft version and reported on its contents, the Justice Department on Friday released the final document. Some details changed — including the number of times the killers were shot, how many shots they fired and how their vehicle was traced — but the overall picture was unaltered.