UVALDE, Texas (KXAN) — The first portion of an after-action report after the deadly mass shooting that killed 19 students and two teachers at Robb Elementary in Uvalde was released Wednesday.

The Advanced Law Enforcement Rapid Response Training Center (ALERRT) of San Marcos released its initial report, which focuses on the events up until the 18-year-old gunman was killed.

The Texas Department of Public Safety previously provided a timeline of the events at Robb Elementary. ALERRT’s report also outlines a detailed timeline of events, before giving its assessment of the physical site of the school building and law enforcement’s tactical response.

According to an officer’s statement in the report, an officer saw the gunman outside of the school. The armed officer asked his supervisor for permission to shoot the suspect. However, the supervisor either did not hear or responded too late. When the officer turned back to the shooter, he had already entered a school hallway.

ALERRT argues the officer would have been “justified in using deadly force to stop the attacker” by the Texas Penal Code, but state standards do not require officers to fire at more than 100 yards away. This officer was around 148 yards away, according to the report.

The report also highlighted another key piece of the attack — the unlocked door into the school.

“Had the exterior door been secured, the suspect may have never gained access to the building. At the very least, the suspect would have been delayed and responding officers would have had more time to find and stop the shooter before he entered the building,” the report said.

The report also said the lock on classroom door 111 was allegedly reported as damaged multiple times.

“We received information from the investigating officer that the lock on room 111 had been reported as damaged multiple times; however, this has not been confirmed through work orders at this time,” the report said.

Texas DPS contacted ALERRT shortly after the attack to assess the response to the Uvalde shooting.

ALERRT was founded in 2002 to provide active attack response training to first responders. The ALERRT research team not only evaluates the efficacy of specific response tactics but also has a long, established history of evaluating the outcomes of active shooter events to inform training

ALERRT said future reports will address the second phase of active shooter response (Stop the Dying) and incident command.

This developing story will be updated.