(NewsNation) — The district attorney in Uvalde County, Texas, has formed a special grand jury to examine the response to the 2022 shooting at Robb Elementary School, sources confirmed to NewsNation.

The shooting killed 19 children and two staff members, and the police response was heavily criticized in the days, weeks and months that followed. The shooter was inside the school for more than 70 minutes before he was shot and killed by police.

On Thursday, the Justice Department issued a scathing report that concluded there were “cascading failures” in the response. It said law enforcement responders “demonstrated no urgency,” with surveillance video showing them waiting in hallways while the gunman went back and forth between two classrooms shooting at teachers and students trapped inside.

The formation of the grand jury was first reported by the local newspaper, the Uvalde Leader-News. According to that report, a dozen people were selected for the panel that is expected to spend at least six months studying the shooting investigation.

“My office continues to methodically and systematically dissect the Texas Rangers investigation of which I have possessed for less than a year. I want to ensure that our efforts in this process are careful, deliberate and fair. I am continuously mindful of my responsibility to the victims, their families, to those under a cloud of accusation and to our community,” District Attorney Christina Mitchell said in a statement to the newspaper.

Regular grand juries review dozens of cases presented by law enforcement and then vote on whether they believe a case has enough evidence to move forward with criminal charges.

In this case, though, the special grand jury will focus on one subject: the Robb shooting. It will serve as an investigative tool for the prosecutor who can subpoena witnesses and other evidence.

At the end of the proceedings, the grand jury makes a recommendation as to any criminal charges that should be pursued. The prosecutor makes a final decision on filing charges.

The Justice Department report identified various points of failure in the shooting response, including failures from leadership, communications issues, inadequate technology and inadequate training.

There have been multiple investigations into the shooting.

The greatest failure, according to the report, was that law enforcement did not recognize the scene as an active shooter situation and should have pushed forward immediately, regardless of the equipment on scene. Since the Columbine High School shooting in 1999, the standard procedure for an active shooter has been that officers should consider stopping the shooter the first priority over everything else, including officer safety.

The investigation found that while some law enforcement officers arrived on the scene three minutes after the shooter entered the school, the focus quickly shifted to treat the situation as one of a barricaded suspect rather than an active shooter despite 911 calls confirming classes were in session and children were present.

Officials who arrived after that received inaccurate information, according to the report, believing the gunman was dead or that school district Police Chief Pete Arredondo was in the room with the suspect.

NewsNation digital producer Stephanie Whiteside contributed to this report.