The May 2022 school shooting in Uvalde, Texas, could have been stopped sooner, according to a new Justice Department report that is set to release nearly 20 months after the massacre.

The police response to the Uvalde school shooting, in which 19 students and two teachers died, was rife with “failure” as law-enforcement officers did not eliminate the gunman in a timely manner, despite quickly arriving to the scene. It took 77 minutes for local police to stop the 18-year-old active shooter after he entered Robb Elementary School, according to the report.

“The response to the May 24, 2022, mass casualty incident at Robb Elementary School was a failure,” the report, a copy of which was obtained by CNN, concludes. The Justice Department will release the full report to the public later Thursday.

The incident is known for officials’ inaccurate assessment of the situation, which the school district police chief initially described as a “barricaded suspect” operation rather than an “active shooter” scenario, which affected how first responders acted that day.

“Officers on scene should have recognized the incident as an active shooter scenario and moved and pushed forward immediately and continuously toward the threat until the room was entered, and the threat was eliminated,” the report states. “That did not occur.”

This inaccurate assessment was the “single most critical tactical failure,” the Justice Department’s Office of Community Oriented Policing Services states.

Law-enforcement officers ran toward the sound of gunfire in the school but then stopped outside the classrooms before killing the shooter, Salvador Ramos.

The Justice Department said its critical-incident review will be publicly released on Thursday “to provide an independent account of law enforcement actions and responses; identify lessons learned and best practices to help first responders prepare for and respond to active shooter events; and provide a roadmap for community safety and engagement before, during, and after such incidents.”