With her constant smile and infectious laugh, people were naturally drawn to Natalie Anne Henderson. Carter J. Davis had the ability to stay positive through adversity, and he was determined to make good grades and play lacrosse in college.

The two 17-year-olds should have been starting their final year of high school. Instead, they were killed behind a north Fulton County shopping center, each by a single gunshot to the head, according to autopsy findings. While two families and two school communities mourned the sudden deaths, Roswell police continued the investigation Tuesday to find the alleged killer.

But the biggest questions remained unanswered: Why were the teenagers behind a grocery store during the early-morning hours Monday? Who was responsible for killing them, and why?

A delivery driver behind the Publix on Woodstock Road spotted the two bodies on the ground beside two vehicles shortly after 6 a.m. and called police. The first officers who arrived at the scene initially believed Natalie and Carter, both of Roswell, had been shot, according to a preliminary police report released Tuesday afternoon. Later Tuesday, the Fulton County Medical Examiner's Office confirmed the teens had been shot, ruling the manner of death homicide for both.

Officers initially suspected the situation may have involved an ex-boyfriend or ex-girlfriend, Officer Zachary Frommer said. But that was only one possibility.

“This information can change quickly as evidence and information is gathered but is only meant to be a starting point,” Frommer said in a statement.

No arrests had been made in the case late Tuesday, but police had several leads, he said.

Both Natalie and Carter were to begin their senior years of high school, school leaders said. Natalie was a member of the color guard at Roswell High School and Carter played football and lacrosse at River Ridge High School in Woodstock, school leaders said. Monday would have been the first day of school for Carter, but Natalie was not scheduled to return until Aug. 8.

But the back-to-school excitement was replaced by tears and hugs as shocked classmates and friends struggled to make sense of the crimes.

Tuesday night, about 200 people — students, parents and members of the community, led by River Ridge lacrosse players — gathered at the school to remember Carter, who wore jersey No. 4 and played the attack position

“They shared some good times and shared some stories that brought tears,” River Ridge principal Darrell Herring said.

A memorial fund was created to honor Carter, who moved to Georgia from Colorado before starting seventh grade when his father made the decision to attend medical school, he posted on an online recruiting blog. The family would move again to South Dakota before returning to Georgia for Carter's junior year of high school.

“But no matter the circumstances, staying positive and working hard will get you where you want to go,” Carter wrote.

About 10 miles away at Roswell High School, marching band practice was canceled both Monday and Tuesday after news of Natalie’s death. Joey Taylor, a former coach for Roswell’s color guard, said Tuesday he remembered when Natalie tried out for a spot with the group. Her family already had vacation plans for the week of band camp, the crucial week for musicians and color guard members. But Natalie assured band directors she deserved a spot.

“I’ll work hard,” she told Taylor. “I’ll get it, I promise.”

She did. And as she got older, she served as a role model to other members of the guard.

“She was always smiling, always laughing,” Taylor said. “Everybody just gravitated toward her.”

Taylor took a job coaching at another school, but he saw Natalie in recent months at a color guard competition. She ran up to him and hugged him.

“She was not afraid to be silly. She was not afraid to be happy,” Taylor said. “She was not afraid to be herself.”

A vigil to honor Natalie is planned Thursday at Roswell High School.