Shocking details about the mass shooting at a Uvalde, Texas, elementary school Tuesday afternoon are emerging, calling into question the response of some law enforcement officials and highlighting the bravery of others.

Salvador Ramos, an 18-year-old who purchased the firearms reportedly used Tuesday days earlier, was running from law enforcement officials after he shot his grandmother and opened fire on a funeral home Tuesday morning. The man entered Robb Elementary School, where he barricaded himself in a classroom and killed 19 children and two teachers.

An unnamed Border Patrol agent later entered the building and killed the shooter.