The police response to the mass shooting at Marjory Stoneman Douglas High School in February was delayed as a result of school officials rewinding a surveillance video, which gave the false impression that the shooter was still in the school for a period of time after he left.

That’s according to a report from the South Florida Sun-Sentinel, which obtained documents showing that then-assistant principal Jeff Morford and security guard Kelvin Greenleaf began watching a live stream of the attack minutes after it had stopped.

Because they did not see the shooter, they then rewound the tape, and proceeded to relay information to Broward Sheriff’s Deputy Scot Peterson, who then relayed information to officers inside responding to the shooting.

Officers were told at one point that the gunman was coming down stairs even though he had exited nearly 30 minutes earlier. That information slowed officers down from making it up to the third floor of the building — they waited in order to ambush the shooter — where several students had been killed or were wounded.

One girl had a pulse when officers arrived, but had died by the time she had been brought out of the building, one deputy said.

“Had we known the shooter wasn't there, we probably could have flooded that building a lot faster knowing that we're just going to go in there and just start trying to recover victims and wounded people”, George Schmidt, a Coral Springs police officer, told investigators.

The delay was discovered months ago, but it has been unclear what caused the error.

Florida shooting – in pictures Show all 10 1 /10 Florida shooting – in pictures Florida shooting – in pictures Police arrest a suspect in connection with the shooting at the Marjory Stoneman Douglas High School in Parkland, Florida Reuters Florida shooting – in pictures Parents wait for news after reports of a shooting at Marjory Stoneman Douglas High School in Parkland, Florida AP Florida shooting – in pictures Anxious family members wait for news of students AP Photo/Wilfredo Lee Florida shooting – in pictures Students being evacuated from the school AP Florida shooting – in pictures Students being evacuated from the school Getty Florida shooting – in pictures People gather waiting for word from students AP Florida shooting – in pictures Parents waiting for news on their children AP Florida shooting – in pictures People gather at a hotel where students were taken after the shooting Getty Florida shooting – in pictures Florida Governor Rick Scott speaks to the media as he visits Marjory Stoneman Douglas High School following the shooting AFP/Getty Florida shooting – in pictures Dr. Igor Nichiporenko, Medical Director Trauma, left, and Dr. Evan Boyer, Medical Director, Emergency Services, speak about treating victims and the suspect at a press conference outside Broward Health North hospital AP

Mr Morford has said that he is unsure if he told Mr Peterson — who relayed the information to the officers in the building — that the information he was giving was old.

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Mr Peterson retired after it was discovered that he failed to enter the building during the shooting. Mr Morford has taken a job at a different school as an investigation is undertaken to determine if he ignored student concerns about the shooter, who had previously been a student at the Parkland, Florida school.