The gunman behind a deadly mass shooting at abarricaded himself inside a classroom and opened fire while teachers broke windows throughout the school to try to save other children, a law enforcement official said Wednesday.
Lt. Christopher Olivarez, of the Texas Department Public Safety, detailed Tuesday's horrific ordeal during an interview with "CBS Mornings" co-host Tony Dokoupil.
He said the 18-year-old shooter stormed Robb Elementary School in the small city of Uvalde shortly after crashing his car in the area and immediately engaged in gunfire with state troopers on the scene. The gunman shot several police officers and then locked himself in a classroom, Olivarez said.
"At that point, [he] just started shooting children and teachers that were inside that classroom, having no regard for human life," Olivarez said. "Just a complete tragedy. An evil person going into the school and killing children for no reason whatsoever."
Authorities said 19 children and two adults were killed in the attack - which is the deadliest school shooting since December 2012, when a gunman opened fire atin Newtown, Connecticut.
The Texas shooter, identified as Salvador Ramos, was killed by law enforcement, authorities said.
Before the attack at Robb Elementary - attended by students from second to fourth grade -the gunman was involved in a domestic disturbance with his grandmother, Olivarez said. The killer shot the woman, fled the home in a car and crashed just outside the school, where he then abandoned the vehicle, the lieutenant said.
The grandmother remained hospitalized Wednesday morning.
Olivarez said state police learned the shooter was making his way into the school and were the first to respond.
"They heard the gunfire," said Olivarez. "They saw the shooter. At that point, they were met with gunfire by the shooter. Several police officers were shot."
As the gunman opened fire inside a classroom, teachers in other rooms began "breaking windows trying to evacuate children to prevent any further loss of life," the lieutenant said.
"The initial officers that were on scene, they were at a point of disadvantage," said Olivarez. "There was no way they were able to make entry, especially with the amount of manpower that was on scene. So at that point, their primary focus was to evacuate as many children as possible."
While helping with the evacuations, officers "kept hearing the gunfire," Olivarez said.
A specialized tactical unit made up of local, state and federal law enforcement officers eventually went into the classroom, Olivarez said. One of those officers was shot, but he has since left the hospital, Olivarez said.
A preliminary investigation indicates the shooter was armed with a handgun, an AR-15 assault weapon and high capacity magazines, law enforcement sources told CBS News. Federal firearm investigators are trying to determine how he obtained the weapons, Olivarez said.
The gunman lived with his grandparents in the Uvalde area and attended a local high school, the lieutenant said. He was unemployed and had no known criminal history or gang affiliation, Olivarez said. The shooter's motive remains under investigation.
"That's what we're still trying to determine - exactly what the motives were, what the indicators were, if there were red flags prior to this mass shooting," Olivarez said.
The shooting comes just 10 days after, described by authorities as "racially motivated," left 10 people dead at a grocery store in Buffalo, New York.
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