I'm seeing he was a suspect, chased into the school
Then started shooting back at the Police (Border Patrol)
Then Border Patrol shot back at him
and that's what killed the children.
Are the Police dumb enough to shoot back at a suspect into a school?   
Edit: Forgot link
Of course this is Daily Mail so could all be wrong.
https://www.dailymail.co.uk/news/ar...lementary-school-campus-plunged-lockdown.html
-  Uvalde Memorial Hospital confirmed that two children were brought in dead on arrival and that they were treating several more following a shooting at Robb Elementary School in Uvalde
 
- A gunman allegedly opened fire at an elementary school after he exchanged gunfire with border patrol agents and barricaded himself in the school, sending the campus into lockdown 
 
- Prior to his arrest the suspect exchanged gunfire with border patrol agents before barricading himself in the school