A January school shooting at Perry High School near Des Moines, Iowa, which left two dead and six injured, was “the product of significant preparation and planning,” by a lone shooter, a new report released by the Dallas County Attorney’s office found.

The report, which outlined the timeline of events, also noted the victims of the shooting appeared to have been chosen “based on immediate availability,” rather than being targeted and that the 17-year-old shooter, Dylan Butler, had likely displayed “warning signs” that went unrecognized or unreported.

“The evidence suggests his actions that morning were indiscriminate and driven by a desire to commit suicide with the hostile intent of taking others with him,” the report states.

Butler entered the school through the main entrance, concealing the weapons he was carrying, and hid inside a student bathroom for about 20 minutes, until the school started to fill up with students and staff. At that point, he emerged and started shooting, the report said.

The investigation determined that the shotgun used by Butler “likely came from a large gun collection within the extended family,” and was taken without the owner’s knowledge. A revolver found on Butler was legally purchased by his father in 2020 and left unsecured in the family home, according to Iowa Department of Public Safety Director Stephan Bayens.

The report also details the heroic actions of Perry High School Principal Dan Marburger, who “with disregard to his own injuries, called out to Butler by name and pleaded with him to stop shooting.”

“I can tell you that he saved lives that day,” Bayens said in a news conference on Friday. “He called the shooter by name, repeatedly. ‘Dylan, don’t do it! Dylan, stop! Dylan, let’s talk!’ after being shot more than once. (…) Every time he called that name out, the shooter heard his name, he looked and turned towards the sound, and when he did that, it diverted his attention from who he was intending to shoot.”

Marburger succumbed to his injuries ten days after the shooting, as CNN previously reported.

After officers responded to the shooting, they found the gunman with a self-inflicted gunshot wound, officials said in January.

The Dallas County attorney’s office noted that the evidence in the case “does not support charges at the state level against anyone.”

“While this decision marks the conclusion of the investigation, the impact of this tragedy on the victims, their families, and the entire community remains profound. We extend our continued support to those affected and will stand by them as the community heals from this devastating loss,” county attorney Jeannine Ritchie wrote.