LEWISTON, Maine — For the family of the Army reservist who carried out a mass shooting across Maine's second-largest city one year ago, dissecting what provoked the deadly rampage has been daunting.

Amid the heartbreak in Lewiston, where 18 people were massacred on the evening of Oct. 25, 2023, at a bowling alley hosting a youth night and a bar where deaf people were playing cornhole, the gunman's family contemplated remaining quietly in the shadows.

But the unspeakable violence inflicted on this community has spurred a very public purpose for the family: bringing awareness to traumatic brain injuries among military members and a call to action for continued research.

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"We want to make sure this doesn't ever, ever happen again to another family," said Nicole Herling, the sister of gunman Robert Card.

Card, 40, was found dead by suicide after an extensive two-day manhunt. A firearms and hand grenade instructor and longtime member of the Army Reserve, Card shared a teenage son with his ex-wife.

In the months leading up to the shooting, members of his family tried to get him help, including reaching out to a veterans crisis hotline about his erratic behavior and also placing multiple calls to his military base. They also noted he had complained about hearing voices when he was fitted for high-powered hearing aids and had a "manic belief" that people were against him. Other family members also alerted local law enforcement, which visited Card's home in the weeks prior to the shooting but did not make contact.

Maine's medical examiner requested a post-mortem study of Card's brain, which was conducted by the Boston University CTE Center. The findings were staggering: There was "evidence of traumatic brain injury," researchers said, which "likely" played a role in his symptoms and aligned with previous studies on the effects of blast injuries.

During a hearing in May as part of an independent state commission's fact-finding investigation, the family members relayed that the researchers who studied his brain said it was "one of the worst" cases they had seen — even in comparison to military personnel who had served in Afghanistan and Iraq.

Card was never deployed in combat. Instead, as a hand grenade instructor, he was subject to potentially thousands of low-level blasts over his military career.

Herling stressed that her brother's traumatic brain injury findings don't fully explain his actions and that a brain injury doesn't mean someone is more likely to commit such violence.

Her husband, James, made clear to the independent commission that any brain injury was not an excuse for Card's behavior or actions, which he called "a wrongful act of evil."

Boston University researchers had said they found no evidence the shooter suffered from chronic traumatic encephalopathy, or CTE, a degenerative brain disease associated with behavioral and cognitive issues related to repeated head injuries.

Still, the conclusion has given Herling a pathway for turning a tragedy into a meaningful mission.

"We had recognized that we needed to help other families, especially once we realized that Robbie's brain had been compromised," Herling said in an interview with NBC News anchor Lester Holt.

Through Card's brain being examined after his death, Herling learned about so-called brain banks, a collection of donated brain tissue used for research and education.

The Herlings are proponents of Project Enlist, an initiative of the Concussion Legacy Foundation, a nonprofit organization in Boston that is recruiting and conducting outreach to the military community to encourage veterans and service members to be part of a brain bank registry.

The research is being done through the UNITE Brain Bank, a collaboration between the Department of Veterans Affairs and Boston University.

The scientific understanding of traumatic brain injuries and related disorders is in its infancy, and having further research of military service members' brains will ultimately help create effective treatments and testing for living patients, said Dr. Chris Nowinski, the CEO and co-founder of the Concussion Legacy Foundation.

Since Project Enlist began in 2018, almost 300 veterans have donated their brains for research, with thousands more pledging to do the same, the group said, with the aim of having increased data similar to how athletes have been studied for CTE and other brain injuries.

"We're just starting to get a handle on which specific military roles are putting people at risk of CTE or repeated blast overpressure," Nowinski said, "and this is not a conversation we were having five years ago."

The Herlings are in the process of launching their own nonprofit organization, Rising Over Brokenness, to help start conversations about mental health awareness and brain injuries among service members. Herling's other brother, Ryan Card, is a retired Army ranger who became disabled as a result of deployments to Iraq and Afghanistan.

During the state commission hearing, Herling spoke openly about their brother's declining state of mind and how "his brain was not healthy."

"Here, I brought the very helmet meant to safeguard my brother's brain," she said, showing the commission the military headgear. "To the Department of Defense: It failed. It's been failing."

The U.S. Army released its own report into the shooting in July, admitting that there were "multiple errors" in how Card's unit handled him in the few months before the shooting as he was hospitalized in a psychiatric unit with reported symptoms of psychosis and homicidal ideations. But the Army report denied that any brain-related injury was linked to his military service.

Still, the military in August announced new guidance to minimize blast exposure among service members. They will conduct "baseline cognitive assessments" for its trainees and develop improved protective equipment.

Last week, lawyers representing 100 survivors and the family members of victims announced the intent to sue the Defense Department, the Army and an Army hospital in West Point, New York, that saw Card last summer for allegedly failing to respond to the warning signs and threats.

The Justice Department declined to comment about the claims.

In a statement, the Army said it remains "deeply saddened" by the shooting and leadership has reviewed the findings from its investigation and "put great effort in implementing all the recommendations and lessons learned."

Officials said the U.S. Army Reserve has completed several actions, including improving communication among a soldier's chain of command related to behavioral health, and is "expeditiously working on implementing additional recommendations."

Herling said she supports any litigation on behalf of the survivors and victims to get "justice and accountability."

Among those who've filed a claim is Leroy Walker Sr., the father of Joseph Walker, a manager at Schemengees Bar and Grille, where he and nine other victims were killed.

Walker credits the gunman's family for treading carefully in the wake of the shooting.

"They've done everything, I think, that they could do to make this easier on everybody," Walker said. "So right from the beginning, I never held anything against them. They're a father and mother that raised a good son. And again, whatever drove him off the deep end, it's not their fault. It's not my fault. It's not your fault. It just happened."

The loss of his son, who was 57, is incalculable, he added.

"Every morning that I get up, he's the first person I think of and pretty much the last person when I go to sleep at night," Walker said. "It's been a tough, tough year."

The Herlings acknowledge that everyone, from their family to the Army to local law enforcement, had a responsibility to ensure Card's firearms were removed from his home as they grew increasingly concerned he might hurt himself or others.

Like Walker, the Herlings are remembering those killed as a reminder of how acutely lives have been altered. The names of all 18 victims — one as young as 14 and others in their 70s — are written on the walls of their home; outside, the names line their property with blue hearts signifying Lewiston.

"I don't ever want to talk about Robbie without acknowledging the pain that he's caused to other people," Nicole Herling said.

Her husband's voice broke as he thought of the children who no longer have their parents and those killed who were simply enjoying a night out before the sounds of laughter and amusement were replaced with panicked screams and cries for help.

"It's hard to hear it," James Herling said, "but we're using this as a fuel to be able to make sure that other people are aware of the struggles that are going on."

Brenda Breslauer reported from Lewiston, and Erik Ortiz from New York.