The plan was simple: Ayanna Maertens Griffin and her boyfriend, Joel Bianda, were to drive to Danville, Va., on Feb. 8, pick up a friend and return to the D.C. area the next day, her father said. But something went horribly amiss along the way.

The two were found dead in the grassy median of a rural stretch of highway in the early hours that Saturday in Halifax County, about 30 minutes from their intended destination. Their car was nearby.

George Ivan Maertens Aramayo said police have not told him why his daughter, 19, and Bianda, 21, were killed. He is not familiar with Mohamed Aly, the 18-year-old from Alexandria who is facing two first-degree murder charges. Aly attended T.C. Williams High School in Alexandria, where friends say he was a strong student and athlete hoping to play college football.

Between the shootings and his arrest at school Thursday, Aly was broadcasting his skill as a cornerback and his workout routine, with no sign of any turmoil.

“Looking for a home to showcase my motivation, dedication, and appreciation to the game,” he wrote on Twitter.

Kennedy Ntiamoah, 20, played the same position as Aly for a rival high school. He said he was baffled by the arrest of the popular, self-possessed younger player, who got good grades and scores on standardized tests. He last saw Aly when he was home from college in December and they played an informal 7-on-7 game.

“If he needed help or anything, he would always reach out. I trained with this dude; I know of him,” Ntiamoah said. “He was always smiling, always happy. . . . I wouldn’t expect him to pull a trigger and kill.”

James Longerbeam, who coached football at T.C. Williams for the past four years, referred all questions to a school spokeswoman, who declined to comment. But on Twitter, his wife, Alette Longerbeam, wrote that she was “really at a loss, really feeling lost. I can’t wrap my head around this.” She had previously described Aly as akin to a son.

Kyla Janay, 16, a fellow student, described Aly in a text message as “a good spirit, a good soul . . . he was a person to light up the room with his smile.”

She said, “This all just doesn’t make sense Mohamed is not this person.”

The killing remains a mystery to Maertens Aramayo as well. He said he spoke with his daughter a few days before she was killed.

“She had passed her learner’s permit,” Maertens Aramayo said on Friday. “There it was in the mailbox. . . . It might be the last picture taken of her.”

Maertens Griffin lived in Fairfax County and had dreamed of attending Virginia Tech to study computer engineering. She worked at Jimmy John’s and was attending classes at Northern Virginia Community College. She and Bianda had dated for about a year, her father said. They both grew up in Germantown, Md., and went to Northwest High School, where Maertens Griffin did well enough to graduate at 16 and skip her senior year.

“That was my pride [that] my daughter was able to skip 12th grade,” Maertens Aramayo said.

Maertens Aramayo said police told him they had recovered Maer­tens Griffin’s and Bianda’s cellphones before Aly’s arrest on Thursday. Maertens Aramayo said police did not tell him where the phones were found and have provided few other details about the case. Maertens Aramayo said if Aly was involved, he wonders how the teen got back to the D.C. area.

Aly’s family could not be reached, and online court records did not yet list a lawyer.

Bianda’s family has declined to comment.

Maertens Aramayo remembers his daughter as “bubbly.” He recalled that when she was 10, a man had opened the door for them at a restaurant, so she gave him a hug.

“She would talk to people randomly,” Maertens Aramayo said. “She had an infectious smile.”

Tragedy struck at what should have been a moment of joy. Maer­tens Aramayo was scheduled to be remarried Monday but called off the wedding. Now, he is planning a funeral for his daughter.

Magda Jean-Louis contributed to this report.