A new report in the Sun Sentinel details the critical minutes leading up to and during February’s mass shooting at Marjory Stoneman Douglas High School in Parkland, Florida; when former student Nikolas Cruz was able to get inside a building at the school and open fire in multiple locations, killing 17 people before escaping the scene by blending in with the evacuating students.

Cruz, then 19, was later apprehended by a local police officer from a neighboring town who spotted him walking through a quiet residential neighborhood near the high school.

The Sun Sentinel report is a minute-by-minute compilation of the afternoon of February 14, when Cruz took an Uber to the school, carrying an AR-15 inside a bag as he entered a freshman building where he would terrorize students and teachers on three separate floors without being apprehended.

The report is critical of Broward County deputies assigned to the school’s security team who failed to confront the shooter, even though some were armed.

In one instance, an unarmed campus monitor appears to have had an opportunity to confront Cruz before he opened fire, but that monitor, David Taylor, was seen on surveillance footage turning away from Cruz after seeing him in a hallway. Taylor reportedly said he had planned to take the stairs at the other end of the hallway to the second floor, where he expected he could intercept Cruz.

The report outlines multiple failures of campus security and school personnel to send a Code Red alert, meaning that the first widespread signal of trouble was a fire alarm set off by gunshots — which sent students and staff into the hallways instead of taking cover inside classrooms.

A misunderstanding and miscommunication about the school’s surveillance video system also may have contributed to the number of casualties. The report notes that responding police officers were not aware that the surveillance footage was on a 20-minute time delay, and believed through communication with the a school security officer and an assistant principal who were monitoring the video that Cruz was still inside a school building when in fact he had escaped by that point. According to the report, the police resources used to search for the shooter meant that injured students did not get medical attention as quickly as they needed it.

For reasons that remain unclear, the Broward County Sheriff’s department did not immediately set up a command post at the school, despite a request from a deputy. Overall, it appears that officers from neighboring Coral Springs Police responded more efficiently and effectively to the shooting, entering the school ahead of Broward County deputies who remained outside the building, some taking cover behind a patrol car.

All told, the gunshots had ended for a full five minutes before any armed law enforcement officers entered the building where the massacre took place.

Read the full report here.

Cruz is in custody at the Broward County Jail awaiting his murder trial, which is expected to begin in 2019.