CHARLOTTE, N.C. — Less than a year after a devastating motorcycle wreck that friends say left him muddled and struggling, Keith Lamont Scott was shot to death by Charlotte police officers who said he refused to drop a gun.

Neurologists say they aren’t surprised that someone with a severe traumatic brain injury would be slow to react and have difficulty following instructions, particularly when orders are being shouted by police officers with their weapons drawn.

“They don’t do well in stressful situations,” said Dr. David Brody, professor of neurology at Washington University in St. Louis. “They often make poor choices or impulsive decisions under stress.”

Brody noted that his comments refer to severe TBIs in general, and that he never saw Scott as a patient. But he said “there’s no way a patient with a TBI who doesn’t know the difference between right and wrong should own a gun or drive a car.”

Scott was killed Sept. 20 by a Charlotte police officer, prompting days of protests that included another man’s shooting death one riotous night. Body camera and dashcam recordings released by the police department show Scott slowly backing out of an SUV. Police say he refused commands to put down a gun.

Graphic, 16-minute video released Tuesday night captures the moments just before and after the shooting, with officers treating Scott’s gunshot wounds and one officer telling his colleague to “stay right here with the gun.” Scott can be heard moaning as officers ask his name and one encourages him to “stay with us.”

Scott’s final moments also were recorded by his wife, Rakeyia, in a video shared widely on social media. She can be heard shouting to police that her husband “doesn’t have a gun, he has a TBI.” She pleads with the officers not to shoot before a burst of gunfire can be heard.

Police Chief Kerr Putney said officers recovered a gun Scott had in his possession, but none of the videos conclusively shows that. Scott’s mother maintains he was holding a Quran.

After running his motorcycle into a tree in November 2015, Scott struggled to recover from two broken hips and a broken pelvis as well as his brain injury, his mother told a TV station.

“You could look at him and tell something was wrong,” said Dana Chapman, a former neighbor. “You could walk up to him; you didn’t have to speak. You could look at him and tell there was a problem.”

Chapman said he would see Scott walking twice a day, leaning on a wooden cane for support. “He had to learn how to talk again, how to walk again,” Chapman said.

Another neighbor, Anthony Spain, said Scott must have zoned out as police were yelling at him.

“He was like a baby,” Spain told the Gaston Gazette, comparing his friend to an Alzheimer’s patient. “They killed a baby.”

TBIs range in their severity. But if Scott had to relearn how to walk and talk, he likely suffered an injury acute enough to permanently affect brain function, according to Jeffrey S. Kutcher, national Director of the Sports Neurology Clinic at the CORE Institute, in Brighton, Mich. That “can lead to devastating changes in behavior, impulse control and really, any cognitive function.”