The U.S. Justice Department said on Sunday it will review law enforcement’s response to the school shooting in Uvalde, Texas, that killed 19 children and two teachers, amid growing anger over why police failed to swiftly confront the gunman.

Uvalde law enforcement agencies allowed the shooter to remain in a classroom at Robb Elementary School for nearly an hour while officers waited in the hallway and children inside made panicked 911 calls for assistance.

Texas state and county authorities say they are conducting their own inquiry. Anthony Coley, a spokesman for the Justice Department, said it will conduct a “Critical Incident Review” of law enforcement’s response to the shooting at the request of Uvalde’s mayor.

“The goal of the review is to provide an independent account of law enforcement actions and responses that day, and to identify lessons learned and best practices to help first responders prepare for and respond to active shooter events,” Coley said.

“The Justice Department will publish a report with its findings at the conclusion of its review,” Coley added.