Last summer, days into a new assignment leading a platoon in a volatile patch of southern Afghanistan, a first lieutenant in the U.S. Army asked one of his soldiers to open fire on two Afghan men on motorcycles.

The fatal shots set in motion an extraordinary criminal investigation that unfolded largely unnoticed until a jury at Fort Bragg, N.C., this week heard dramatically different accounts of the choices that the officer, Clint Lorance, made that day.

On Thursday evening, jurors convicted the 28-year-old Lorance of murder, siding with prosecutors who portrayed his order as a reckless contravention of the rules of engagement. Lorance’s supporters say the real crime was the military’s decision to turn a war hero deployed in one of the most dangerous and remote corners of Afghanistan into a defendant.

“To put murder charges on him!” Lorance’s mother, Anna Lorance, protested in an interview before the verdict in the court-martial was announced. “In war, people die. When you’re in a heated combat zone, you have seconds to think.”

Lorance was sentenced to 20 years in prison, forfeiture of pay and dismissal from the military.

In the annals of American war crimes in Iraq and Afghanistan, cases that have landed service members in court on serious charges have typically been preceded by outcries, allegations of egregious conduct and extensive coverage in the news media. The vast majority of defendants have been enlisted troops.

There was the 2004 Abu Ghraib prison scandal and the 2005 Haditha massacre in Iraq — cases so shocking that they injected an indelible poison into the relationship between Baghdad and Washington. In Afghanistan, a squad of soldiers infamously described itself as a “kill team” for shooting Afghan men for sport in 2010; the group’s ringleader kept body parts as trophies. Just months before Lorance’s fateful patrol, an Army sergeant left his base at night and massacred 17 sleeping Afghans, including several children.

Lorance’s case is remarkable because he is only the second Army officer charged with murder in a battlefield death during the wars in Iraq and Afghanistan. His defense, outlined in a detailed account on a Web site registered to his name, sought to shift the burden, putting U.S. military rules of engagement on trial.

“In modern warfare, there is no clearly defined enemy,” argues a statement on the site, which his family is using to raise money for the officer’s legal expenses. “Long gone are the days where American Soldiers could distinguish their enemy by the uniform they wore.”

Lorance was born and raised in Hobart, a small town in Oklahoma, the son of a welder and a stay-at-home mom. As a toddler, his mother said, he played with toy guns and firetrucks. “We knew at a young age who he was going to be: someone who would defend and help,” she said.

He signed up to become a military police officer on his 18th birthday, when the nation was barely a year into the Afghanistan war and had not yet invaded Iraq. As an enlisted man, Lorance was deployed to South Korea and later Iraq, where he spent 15 months. He loved the rigor and intensity of a military career, Anna Lorance, 54, said.

“Every year, his pride just grew and grew, along with his rank,” his mother said.

After his Iraq deployment, Lorance became the first college graduate in his family and was commissioned as an officer.

He was deployed to southern Afghanistan in March 2012. After a first lieutenant in his unit, the 4th Brigade Combat Team of the 8nd Airborne Division, was wounded in a bombing, Lorance unexpectedly became a platoon leader, a job that many infantry officers regard as among the most challenging and rewarding in a military career.

Shortly after he and his men rolled out of their small outpost in Kandahar province early July 2, 2012, Army pilots warned Lorance over the radio about suspected insurgents loitering north, east and west of the platoon, according to the account posted on the Web site. As the troops, most of whom were on foot, approached a village, they spotted the men on motorcycles. Suspecting that they were insurgents, Lorance asked one of his soldiers to shoot them.

“I was given a lawful order,” the shooter, Pvt. David Shilo, testified, according to the Fayetteville Observer. “My life wasn’t threatened at the time.”

Lorance’s site contends that intelligence reports he had reviewed suggested that every man on a motorcycle in that vicinity was presumed to be a member of the Taliban because the insurgent group was in control of the area. The order to fire the two long-range shots was rightful, his account says, “eliminating the threat.”

Prosecutors say Lorance knew that to be false — and they elicited testimony from service members that bolstered their case. U.S. troops in Afghanistan may open fire only if they detect hostile intent or actions in the battlefield.

After some of his men reported the incident up the chain of command, Lorance was reassigned to a desk job and stripped of his weapon as an investigation was launched. In January, a few months after returning home with the rest of the brigade, he was charged with murder, attempted murder and misconduct.

The charging document depicts Lorance as abusive. He warned an Afghan man whose property abutted the outpost that “if there is enemy activity on your land, we will shoot and kill you, your family and your kid,” the document says. It also accuses him of impeding the investigation by asking a soldier to falsely state in the incident report that the platoon could not examine the slain Afghans’ bodies because locals removed them shortly after the shooting.

His parents raised money through the Web site and their neighbors to retain Guy Womack, a Houston lawyer and retired Marine lieutenant colonel who has represented high-profile military defendants.

Womack said in a statement issued late Thursday night that he was “bitterly disappointed” by the verdict. He said his client’s actions were justified in light of the threat level in the area and the information conveyed to him during the patrol, which made Lorance feel the men in motorcycles posed an imminent threat.

“I respect the Member’s decision,” Womack wrote, referring to the jury. “But I fear it bodes ill for other small unit leaders who face similar challenges, daily, in Afghanistan.”

The sentence handed down against Lorance dashes his plans for the future.

“Until this incident, Clint planned on serving his country for 10 more years, retiring from the Army and attending law school,” his Web site says. “Clint’s dream is to work in a district attorney’s office as an associate prosecutor.”