PORSMOUTH, N.H. — Army Reserve and law enforcement officials failed to take several opportunities that could have prevented the Lewiston, Maine, mass shootings last year, an independent commission tasked with investigating the tragedy said in its final report Tuesday.

The commission, formed last year by Maine Gov. Janet Mills, was comprised of several attorneys, a forensic psychologist, and a psychiatrist who released its final report Tuesday about the October 2023 mass shootings in Lewiston, Maine, that left 18 people dead. In the report, the commission said that while the actions of the shooter, Robert Card, were his own, his Army reserve unit and local law enforcement missed opportunities to intervene after several concerns about Card's behavior were raised.

Daniel Wathen, a retired Chief Justice of the Maine Supreme Judicial Court and the commission's chair, spoke on behalf of the group during the news conference Tuesday. He said the commission was only tasked with investigating the facts of the shootings, not making recommendations, adding that it is impossible to know whether the shootings would have been prevented if officials had properly intervened.

The report said authorities “failed to undertake necessary steps to reduce the threat he posed to the public." The independent commission added in its final report that police officers should have undergone steps to seize Card's firearms through Maine's yellow flag law.

Maine's yellow flag law allows anyone who suspects a gun owner is a threat to report them to the police, who then must determine whether that person should be taken into protective custody, evaluated by a mental health professional, or apply for a court order to seize their firearms. Several people who knew Card, including his son and former wife, notified law enforcement about concerns about his behaviors in the months leading up to the shooting, the report said.

As a result, local police officers had reason to utilize their power under the state's yellow flag laws before the shooting, the report said, reiterating a previous finding in the commission's interim report from this year. The report said that police officers who testified in front of the commission said the yellow flag law is "cumbersome, inefficient and unduly restrictive."

Report: Army Reserve officers did not tell police about all of Robert Card's threatening behavior

The report also said officers in the Army Reserve, which Card was active in, failed to take steps to reduce the threat he posed to the public. The report found that Army Reserve officers were aware of Card's concerning behavior, including hallucinations, aggressiveness, and ominous comments but did not notify local police officers about the full extent of the behavior.

According to the report, several of Card's family members, friends, and fellow reservists alerted Army Reserve officials about concerning behavior. "Despite their knowledge, they ignored the strong recommendations of Card’s Army mental health providers to stay engaged with his care and 'mak[e] sure that steps are taken to remove weapons' from his home,'" the report added.

The commission said that if Army Reserve officers had notified police officers of the extent of Card's behavior, they may have acted "more assertively."

What happened in Lewiston

On Oct. 25, the 40-year-old Army reservist opened fire at a bar and bowling alley in Lewiston, killing 18 people and wounding 13. Days later, after an intense search that kept residents across the city locked in their homes, authorities found Card dead of a gunshot wound.

A post-mortem analysis of Robert Card's brain by Boston University's CTE Center, completed at the request of the Maine Chief Medical Examiner’s Office, revealed "significant evidence of traumatic brain injuries at the time of the shootings." Card's family made the findings public and declined to comment.

Among the injuries recorded by researchers were damage to the fibers that allow communication between areas of the brain, inflammation and a small blood vessel injury, according to the report signed by Dr. Ann McKee, director of the lab at Boston University, and released Wednesday. She said there was no evidence of chronic traumatic encephalopathy (CTE), a brain disease often found in athletes and military veterans who have suffered repetitive head trauma.

"While I cannot say with certainty that these pathological findings underlie Mr. Card’s behavioral changes in the last 10 months of life, based on our previous work, brain injury likely played a role in his symptoms," said Dr. Ann McKee, director of the lab at Boston University, earlier this year.

Contributing: Christopher Cann, Minnah Arshad, and Adrianna Rodriguez, USA TODAY