UVALDE, Texas (KXAN) — A police officer armed with a rifle watched the gunman in the Uvalde elementary school massacre walk toward the campus but did not fire while waiting for permission from a supervisor to shoot, according to a sweeping critique released Wednesday on the tactical response to the May massacre.

The first portion of the after-action report on the shooting that killed 19 students and two teachers at Robb Elementary was released Wednesday. The report, by the Advanced Law Enforcement Rapid Response Training Center (ALERRT), focuses on the events up until the 18-year-old gunman was killed.

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, the report said.

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.

The Texas Department of Public Safety contacted ALERRT shortly after the attack to assess the response to the Uvalde shooting. DPS also previously provided a timeline of the events at Robb Elementary.

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.

Authors of the 26-page report said their findings were based off video taken from the school, police body cameras, testimony from officers on the scene and statements from investigators.

Also among their findings:

— It appeared that no officer waiting in the hallway during the shooting ever tested to see if the door to the classroom was locked. The head of Texas’ state police agency has also faulted officers on the scene for not checking the doors.

— The officers had “weapons (including rifles), body armor (which may or may not have been rated to stop rifle rounds), training, and backup. The victims in the classrooms had none of these things.”

— When officers finally entered the classroom at 12:50 p.m. — more than an hour after the shooting began — they were no better equipped to confront the gunman than they had been up to that point.

—”Effective incident command” never appears to have been established among the multiple law enforcement agencies that responded to the shooting.

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

The Associated Press contributed to this report.