Tarreece Sampson’s mother recalled the day her son laid out how he wanted to spend his life. He would become a principal and open a community center for troubled children. Johnna Tyler Davis recalled him saying, “Mommy, I found my purpose.”

Davis testified about the moment Friday in a Fairfax County courtroom, just feet from one of the men, who was later sentenced to 20 years in prison for ending Sampson’s life even as he was earnestly trying to realize his calling.

Sampson, 24, a Fairfax County teacher’s aide and graduate student at George Mason University, happened upon Charles Edward Benson and another man as they were robbing cars in the parking lot of his Fairfax County apartment complex in May 2016. Sampson was shot, his final moments heard by a friend he had called.

Family members testified the senselessness of the killing was heightened by the exemplary life that “TJ,” as they called him, had lived. His mother recalled how he gave his last dollar to a homeless person on a high school trip to the District. He mentored children and was getting a degree in special education.

“Breathing is different. It’s filled with pain. It’s as if you learn how to function, but there’s a really big hole in your heart. It just bleeds all the time,” Davis said. “I never stop hurting. I never stop aching.”

Later, Benson, of the District, rose in a red-and-white-striped jail jumpsuit and offered a halting apology before he was sentenced: “I ask you all to please find it in your heart to forgive me.”

But Fairfax County Circuit Court Judge Michael F. Devine said he was unimpressed by Benson’s attempt at contrition.

“TJ was an outstanding member of this community. Now, he is gone for no reason,” Devine told Benson. “You don’t have the right to ask for forgiveness. You have to earn the right to forgiveness.”

The events that led to the courtroom unfolded in the early hours of May 20, 2016. Sampson and a friend had gone out to a hookah bar, before he returned to the Cityside apartments in the Huntington area of Fairfax County.

Travis Cuffey, the friend, testified at a previous hearing the friends had a habit of calling each other to say they had arrived home safe after nights out. Sampson called Cuffey from the front of his apartment building that night.

“Hey, are you good?” Cuffey told a Fairfax County courtroom he heard Sampson ask someone. Then, he heard a single shot. Cuffey said Sampson said he had been shot, before he heard a gurgling sound. Sampson never spoke another word.

Cuffey hung up and called 911, but when police arrived on the scene there was little they could do. Sampson was suffering from a gunshot wound to the chest and was left to bleed out on the asphalt. He was pronounced dead.

Assistant Commonwealth’s Attorney Kathryn A. Pavluchuk said that before the shooting Benson had handed a gun to the other man convicted in Sampson’s slaying, Tre’Sur Hawkins, of the District, who opened fire on the teacher’s aide.

A lengthy two-year investigation would follow as Fairfax County police tried to track down the culprits. Benson was tied to the crime after a fingerprint lifted from the door handle of a car in the parking lot of Sampson’s complex matched his thumbprint.

Benson, who was also on probation, was wearing an ankle bracelet that put him at the scene of the crime. A relative of Benson’s testified at an earlier hearing that Hawkins told him he shot Sampson.

Both Benson and Hawkins pleaded guilty to charges of second-degree murder and robbery earlier this year. Hawkins is scheduled to be sentenced in February.