After a 40-year-old Army Reservist named Robert Card went on a shooting spree in Lewiston, Maine, in October, his community grasped for answers.
Eighteen people were killed. Neighborhoods were locked down for days as the police hunted for Mr. Card. Then, after he was found dead from a self-inflicted gunshot wound, his family and fellow soldiers revealed that he had become delusional, paranoid and potentially violent, and that the police had not acted on their warnings about him for months.
Why he unraveled remains a mystery. But the authorities have started to explore one possible answer: that Mr. Card’s brain may have been damaged by his time in the Army.
In recent weeks, the state medical examiner has sent part of Mr. Card’s brain to a laboratory that analyzes brains for maladies caused by repeated hits to the head, including chronic traumatic encephalopathy, or C.T.E. And Army investigators have asked members of Mr. Card’s battalion if his work in the military could have affected his mental state, two soldiers who served with him said.
Publicly, the Army has said almost nothing about Mr. Card’s time in uniform — only that he was trained as a petroleum supply specialist and never deployed to combat. But soldiers who spoke to The New York Times said that description left out something crucial: Mr. Card worked every summer for years as an instructor at an Army hand grenade training range, where he was rocked by thousands of brain-jarring explosions.
For generations, the military assumed that the blast waves that troops experienced from firing weapons or throwing grenades in training posed no danger to them. It is only in the last few years that increasing evidence of harm from repeated exposure, along with mandates from Congress, has driven the Defense Department to start trying to track, study and understand the impact of blast exposure.
An investigation by The Times this fall found that many artillery soldiers who fired thousands of 155-millimeter howitzer rounds developed brain injuries and suffered panic attacks, depression and, in a few cases, hallucinations.
Mr. Card was a sergeant first class assigned to the Army Reserve’s 3rd Battalion, 304th Regiment, a training unit based in Maine that runs a two-week summer field course for cadets from the U.S. Military Academy at West Point, teaching them how to use rifles, machine guns, anti-tank weapons and grenades. Mr. Card joined the unit in 2014, the Army said.
One senior member of the platoon who worked with Mr. Card for years, and asked not to be named because the Army told soldiers not to speak to the media about him, said that as an instructor, Mr. Card worked with grenade launchers, AT4 anti-tank weapons and machine guns, but spent the vast majority of his time on the hand grenade range.
Each summer, all 1,200 West Point cadets have to throw at least one M67 grenade. Most throw two. Mr. Card was nearly always one of the instructors with the cadets in the grenade pits. The soldiers from his unit said he could easily have been exposed to more than 10,000 blasts in all.
The Army did not respond to repeated requests for details about Mr. Card’s work in uniform.
“The concussion from the grenade is brutal, brutal — it will shake your heart,” the senior platoon member said. “We have a berm at the range that protects from shrapnel, but it doesn’t protect from the blast. Some guys got a lot. Probably too much.”
By age 39, Mr. Card was wearing hearing aids.
The senior soldier said that he, too, had hearing trouble, along with headaches and vertigo, and had not slept well in years — all conditions often associated with blast injuries. He added that another longtime soldier in the unit had to be pulled off the grenade training range in 2022 because of mental health concerns. That soldier is currently in a psychiatric hospital, a member of his family said.
“Is it related? I don’t know,” the senior soldier said. “But I know he was right there in the grenade pits with Card.”
Researchers have found a unique pattern of damage in the brains of a number of deceased veterans who were exposed to blasts, but there is no way to detect that damage in living troops. And even if it could be detected, there is no way to predict when the damage might cause a psychiatric disorder, or who might be prone to violence.
Even though so much remains unknown, members of Mr. Card’s platoon said they were concerned that simple steps were not being taken to protect soldiers from blasts.
Blast injuries can cause behavioral changes including insomnia, anxiety, mood swings and substance abuse. Some studies suggest that traumatic brain injuries increase the risk of psychosis, but the evidence is limited.
The military tests all troops who deploy to war zones — even those in desk jobs — for signs of brain injuries when they return. But it does not test instructors who work on training ranges, even though they may be exposed to far more blasts than troops in war zones are.
Mr. Card never deployed, so he never was tested, the senior platoon member said.
Maine’s medical examiner sent Mr. Card’s brain tissue to Boston University, which has the nation’s largest brain bank focused on C.T.E.
“In an event such as this, people are left with more questions than answers,” said a spokeswoman for the Maine Office of Chief Medical Examiner, Lindsey Chasteen. “It is our belief that if we can conduct testing that may shed light on some of those answers, we have a responsibility to do that.”
Detecting C.T.E. would not put to rest questions about what drove Mr. Card’s actions. Experts say people who commit mass violence usually do so for complex reasons that rarely hinge on a single factor.
A spokeswoman for Boston University declined to comment, saying the university could not discuss specific cases without the written consent of the family. Mr. Card’s family did not respond to requests for comment.
Years before Mr. Card became delusional, the Army had indications that grenade ranges were taking a toll on soldiers. In 2015, an Army research team went to the grenade range at Fort Jackson, S.C., after instructors there complained of headaches, fatigue, memory issues and confusion. In 2017, the Army investigated again after receiving more complaints from instructors at Fort Moore, Ga.
“They had instructors who would leave the range, have to stop their car on the side of the road and throw up,” said Gary Kamimori, a retired Army researcher involved in both studies. “They had all the symptoms of concussion.”
The research team placed sensors in the pits to measure blasts. They found that the concussive force from each grenade explosion largely dissipated by the time it reached the pits, but not the sound wave generated when the explosion created a sonic boom. The soldiers in the pits were being hit by sound waves measuring up to 160 decibels — several times more intense than the sound energy of a jet engine.
“Above 140 decibels, sound can vibrate bone. You feel your body shake,” Mr. Kamimori said. “The skull is bone. You are vibrating the brain, the nerves, the connections. Any of those connections get screwed up, you got problems.”
After Mr. Kamimori shared his findings, he said, some ranges altered their schedules to limit individuals’ blast exposure, but the Army did not take any forcewide action. Nor did it continue the research. During the studies, the team collected blood samples from instructors to check for chemical evidence of brain injuries, but with no further funding, the samples were never tested. Mr. Kamimori said they were still sitting in an Army freezer.
Early this year, just before Mr. Card turned 40, he started complaining that voices were accusing him of being a pedophile, his relatives and fellow soldiers told the police. Bouts of paranoia and delusion over the next few months led to him being hospitalized by the Army for two weeks in July.
It’s extremely rare for someone to have a first outbreak of psychosis at age 40, according to Dr. Stephen Xenakis, a psychiatrist and retired Army brigadier general. The condition most often appears when people are young adults.
“If someone has their first psychotic breakthrough at 40, that’s really unusual,” he said. “If he’s my patient, I’m asking what else might be going on that could cause it.”
Military psychologists for generations have noticed that a surprising number of high-performing soldiers tended to become erratic and self-destructive, and were plagued by anxiety, insomnia and difficulty concentrating as they neared retirement in their 40s. It was so commonplace that doctors even had a label for it, Old Soldier Syndrome.
In a 1965 article in the journal Military Medicine, an Army psychologist suggested that the symptoms were caused by fear of retirement. Later generations of military psychologists were more likely to ascribe them to combat exposure and latent post-traumatic stress disorder.
It is only recently that a group of psychologists has suggested that years of weapons blast exposure might be to blame.
A 2021 paper documented Operator Syndrome — a widespread pattern of behavioral and physical problems among career Navy SEALs and other special operations troops — and argued that brain injury, both from enemy blasts and from the operators’ own weapons, lay at the root of most of the problems.
“It wasn’t PTSD, it wasn’t based on a fear response — it was something else,” said Chris Frueh, a professor of psychology at the University of Hawaii and the lead author of the paper. “There is no question in my mind that blast plays a big part in that.”