A Uvalde, Texas, police officer armed with a rifle spotted the gunman outside of Robb Elementary School before he entered the building and asked his supervisor for permission to shoot, but the supervisor either didn't hear the request or didn't respond in time, allowing the suspect to enter the school, according to a report released Wednesday by the Advanced Law Enforcement Rapid Response Training Center (ALERRT).
The gunman would go on to murder 19 children and two teachers before a Border Patrol tactical team eventually breached the classroom and took him out over 70 minutes later, a delay that has been sharply criticized by lawmakers, state law enforcement officials, and the Uvalde community.
It's unclear why the initial Uvalde police officer did not immediately fire at the gunman, who had already started shooting into classrooms as he walked along the perimeter of the school.
"In this instance, the UPD officer would have heard gunshots and/or reports of gunshots and observed an individual approaching the school building armed with a rifle. A reasonable officer would conclude in this case, based upon the totality of the circumstances, that use of deadly force was warranted," the ALERRT center, which is based at Texas State University and provides active shooter response training, wrote in the report.
The officer told investigators that he was concerned about putting children in danger if he missed, but ALERRT noted that the Texas Penal Code says "an individual is justified in using deadly force when the individual reasonably believes the deadly force is immediately necessary to prevent the commission of murder."
The officer was about 148 yards away from the exterior door that the gunman entered, which is well within the range of an AR-15 platform rifle, though patrol rifle qualifications in Texas do not require officers to fire at targets farther away than 100 yards, according to ALERRT.
Two other key mistakes were also made that allowed the gunman to enter the building.
A different Uvalde school district police officer drove by the gunman in the parking lot at a high rate of speed and didn't see him before the suspect entered the school at 11:33 a.m.
Third, a teacher closed the exterior door minutes before the gunman entered, but didn't check to see if the door was locked. Furthermore, even if she did check the door, she didn't have the proper key at the time to lock it.
"If any of these three key issues had worked out differently, they could have stopped the tragedy that followed," ALERRT wrote.
The active shooter training center went on to note three key issues once the gunman was inside the school, including that the classroom door's lock was broken; two teams of officers were stationed at each end of the hallway, creating the possibility of friendly fire striking an officer; and police lost "momentum" once the suspect fired at the first officers to approach the classroom door.
"There is a chance that officers will be shot, injured, or even killed while responding. This is something that every officer should be acutely aware of when they become a law enforcement officer," ALERRT wrote.