TAMPA, Fla. — As an Army sniper in Iraq and Afghanistan, Gabriel Brown craved danger. Combat satisfied what he called his "adrenaline addiction."

When he returned home to Florida, nothing in civilian life provided the sense of invincibility that made combat so alluring and vital. The sniper was now a nursing student. There was a hole in his life, but he found a way to fill it: robbing banks.

He robbed with a military flair. On Feb. 5, 2013, Brown whipped out a gun and tossed an M83 military smoke grenade during a robbery of a TD Bank branch in Auburndale, Fla., that netted $19,000. It was his final crime in a two-week string of robberies that targeted banks, a cellphone store and an insurance company.

Brown was arrested the next day on federal charges that carry a mandatory minimum sentence of 32 years to life. He quickly confessed.

"It was extremely hard for me to find a way to go from being in highly threatening situations, risking my life every day, to sitting at home watching TV alone," he wrote later. "The adrenaline I got from committing robberies was some kind of weird addiction I so desperately needed to get myself out of this depressive state I was in."

Like thousands of other combat veterans, Brown was diagnosed with post-traumatic stress disorder. And like thousands of PTSD veterans seeking reduced sentences for crimes, he blamed the condition, in part, for his actions.

Increasingly, veterans across the U.S. have cited stress related to their combat experience as the reason for civilian misdeeds, a tactic that often reduces or even eliminates sentences for minor crimes, especially in special veterans' courts.

"It's a growing trend, with the stigma of PTSD largely eliminated and the condition more widely understood," said David Frakt, a law professor and Air Force Reserve military legal officer.

But blaming PTSD for serious felonies rarely succeeds, even for elite soldiers like Brown, 34, a decorated Green Beret with no previous criminal record. Courts are aware that most PTSD veterans manage not to commit serious crimes, said Victor Hansen, a law professor and former Army legal officer.

The result of Brown's plea for clemency was different — so different that Hansen and other legal experts could recall no case like it.

In a federal courtroom in downtown Tampa last month, Brown faced sentencing after pleading guilty and testifying against a fellow veteran, Robert McChristian, who was sentenced to 30 years in prison. He cut a sympathetic figure: a powerfully built war hero with a shaved head, military bearing, exemplary combat record and a powerful sense of remorse.

In the gallery was Maria Suarez, his ex-wife and mother of their two children, who divorced him after he signed up as a private security officer for CIA operatives in Pakistan when he left the Army. She dabbed at her eyes with a tissue. Beside Suarez was Brown's mother, a small woman fighting to hold back tears, and his stepfather, a thin, mustachioed Arkansas truck driver.

Brown's family believed PTSD drove him to crime after contributing to his alcohol and drug abuse, depression, nightmares and compulsive gambling. He wouldn't have been the first: A 2012 survey of 1,400 veterans diagnosed with PTSD found that 23% committed crimes, mostly nonviolent, after deployment, according to the Journal of Consulting and Clinical Psychology.

Family members said Brown's personality changed as he struggled to cope with civilian life after 10 years in the Army and four more in Pakistan.

"That wasn't my son — my baby boy. He was distant and angry and threw fits," said his mother, Debby Barrack, who signed for Brown to join the Army at 17.

"He'd never done anything like that, not my little brother. He's always been such a good man and good father," said his sister, Sandra.

Brown's ex-wife wept as she told the judge how Brown drove their children 16 hours to Arkansas every Christmas to visit his parents. Brown is their children's "superhero," she said; his criminal life was "completely out of character for him." He had refused previous treatment for his combat stress, she said, because "this was like a sign of weakness and he wanted to be the brave hero he was paid to be."

Brown had seemed to drag home a troubled life from Afghanistan and Pakistan. He suffered brain trauma from being knocked unconscious by a 50-caliber gun barrel in Afghanistan. He was diagnosed with depression and bipolar disorder. He gambled away $48,000 in a single night. Twice, he tried to commit suicide by taking Xanax or sleeping pills.

While in prison awaiting trial, Brown wrote letters of apology to every person he robbed, though no one had been injured.

"I want you to understand how sorry I am that I scared you," he wrote.