Police officers responding to Tuesday's deadly mass shooting in Uvalde, Texas, were stalled as they entered Robb Elementary School due to uncertainty about the gunman's location, a Texas Department of Public Safety official said.

Lt. Chris Olivarez provided some insight Thursday as outrage and questions mount regarding what took law enforcement so long to stop the gunman, who was in the school for up to an hour and killed 21 people, including 19 children and two teachers, in one classroom. More than a dozen others were injured.

CNN's Wolf Blitzer asked if "current best practices" call for officers to disable a shooter as quickly as possible regardless of how many officers are on site.


"Correct," Olivarez said.

"The active shooter situation — you want to stop the killing. You want to preserve life. But also one thing that, of course, the American people need to understand is that officers are making entry into this building. They do not know where the gunman is," he added. "They are hearing gunshots, they are receiving gunshots. At that point, if they proceeded any further not knowing where this suspect was at, they could have been shot — they could have been killed. And at that point, that gunman would have the opportunity to kill other people inside that school."

Three officers initially breached the school through the same door as the shooter, where he said officers were "taking gunfire." At that point, they called for tactical teams and additional backup "that could arrive to assist not only with the situation but also to assist in evacuating students and teachers," Olivarez said.

Eventually, backup did arrive. A member of a Border Patrol tactical unit that arrived later on has been credited with killing the shooter, identified by authorities as 18-year-old Salvador Ramos, after breaching the classroom in which he was barricaded. Olivarez said they were assisted by local officers who arrived with ballistic shields and noted that at least one Border Patrol agent received minor injuries in the raid. Officials said the gunman used a rifle in the massacre and also shot and wounded his grandmother before the attack on the school.


Earlier Thursday, Texas officials walked back earlier claims that a school officer engaged Ramos before Ramos entered the building.

"It was reported that a school district police officer confronted the suspect that was making entry. Not accurate. He walked in unobstructed initially," said Victor Escalon, South Texas regional director for the Department of Public Safety. "So from the grandmother's house to the car ditch to the school, into the school, he was not confronted by anybody, to clear the record on that. Four minutes later, law enforcement are coming in to solve this problem."

The shooting is still under investigation.