AUGUSTA, Maine (AP) — Robert Card, an Army reservist who shot and killed 18 people in Maine last year, had significant evidence of traumatic brain injuries, according to a brain tissue analysis by researchers from Boston University that was released Wednesday.

There was degeneration in the nerve fibers that allow for communication between different areas of the brain, inflammation and small blood vessel injury, according to Dr. Ann McKee of Boston University’s Chronic Traumatic Encephalopathy (CTE) Center. The analysis was released by Card’s family.

Card had been an instructor at an Army hand grenade training range, where it is believed he was exposed to thousands of low-level blasts.

“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,” McKee said in the statement from the family.

Card’s family members also apologized for the attack in the statement, saying they are heartbroken for the victims, survivors and their loved ones.

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Army officials will testify Thursday before a special commission investigating the deadliest mass shooting in Maine history.

The commission, established by Democratic Gov. Janet Mills, is reviewing the facts surrounding the Oct. 25 shootings that killed 18 people in a bowling alley and at a restaurant and bar in Lewiston. The panel, which includes former judges and prosecutors, is also reviewing the police response to the shootings.

Police and the Army were both warned that shooter, Card, was suffering from deteriorating mental health in the months that preceded the shootings.

Some of the 40-year-old Card’s relatives warned police that he was displaying paranoid behavior and they were concerned about his access to guns. Body camera video of police interviews with reservists before Card’s two-week hospitalization in upstate New York last summer also showed fellow reservists expressing worry and alarm about his behavior and weight loss.

Card was hospitalized in July after he shoved a fellow reservist and locked himself in a motel room during training. Later, in September, a fellow reservist told an Army superior he was concerned Card was going to “snap and do a mass shooting.”

Card was found dead of a self-inflicted gunshot wound after the biggest search in state history. Victims’ families, politicians, gun control advocates and others have said in the months since the shootings that law enforcement missed several opportunities to intercede and remove guns from Card. They’ve also raised questions about the state’s mental health system.

Thursday’s hearing in Augusta is the seventh and final one currently slated for the commission. Commission chair Daniel Wathen said at a hearing with victims earlier this week that an interim report could be released by April 1.

Wathen said during the session with victims that the commission’s hearings have been critical to unraveling the case.

“This was a great tragedy for you folks, unbelievable,” Wathen said during Monday’s hearing. “But I think has affected everybody in Maine and beyond.”

In previous hearings, law enforcement officials have defended the approach they took with Card in the months before the shootings. Members of the Sagadahoc County Sheriff’s Office testified that the state’s yellow flag law makes it difficult to remove guns from a potentially dangerous person.

Democrats in Maine are looking to make changes to the state’s gun laws in the wake of the shootings. Mills wants to change state law to allow law enforcement to go directly to a judge to seek a protective custody warrant to take a dangerous person into custody to remove weapons.

Other Democrats in Maine have proposed a 72-hour waiting period for most gun purchases. Gun control advocates held a rally for gun safety in Augusta earlier this week.

“Gun violence represents a significant public health emergency. It’s through a combination of meaningful gun safety reform and public health investment that we can best keep our communities safe,” said Nacole Palmer, executive director of the Maine Gun Safety Coalition.

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Whittle reported from Portland.