The aunt of missing Ridge View High School cheerleader Gabrielle Swainson said Wednesday her disappearance is impossible to understand.

“She’s just a wonderful child, an A-student, she plays the guitar, she’s on a jazz-tap dancing team that does statewide competitions,” said Tara Swainson, 41, who said it’s completely out of character for her niece to go missing.

“I just really hope that we find her and find her safe and alive. I can’t imagine she would willingly be gone.”

Richland County Sheriff Leon Lott has activated his major crimes unit – a team of veteran investigators, replacing the missing persons unit that initially handled the case. He said Wednesday he is highly concerned about the 15-year-old girl’s vanishing with no trace.

“We’ve put our best people on this,” Lott said in an interview. “We’re going to work this like it’s something bad, in hopes that it turns out to be something good.”

Gabrielle hasn’t been seen since her mother, Elvia Swainson, a single mom, left her in their two-story house at 221 Tamara Way alone on Saturday and went to work early, around 3 a.m., Richland County deputies said. Gabrielle is her only child.

When the mother came back shortly after 7 a.m. Saturday, she heard her daughter’s alarm going off in her second-floor bedroom. But her daughter wasn’t in the house.

Tara Swainson said that was the first time that Elvia Swainson had left her daughter alone in the house that early in the morning. “She and Gabbiee stayed up really late, watching movies, riding out a thunderstorm that night.” Gabrielle was sleeping in her second-story bedroom when her mother left, Tara Swainson said.

“The one time she decides to go to the office in the wee hours of the morning, this tragic thing happens,” Tara Swainson said. The mother went into the office to catch up on some back work she was worried about, she said.

Robert Platts, 49, a neighbor who lives across the street from the Swainsons, said Elvia Swainson came to his house about 7:15 a.m. Saturday to ask if he’d seen her daughter.

“She (Elvia Swainson) was upset,” said Platts, who with his wife, Tammy, has known the Swainsons for years. Mother and daughter were always together, he said. Those times in the afternoon when Gabrielle was home alone, she sometimes had girlfriends over but that was it.

“She (Gabrielle) is just a really nice young girl,” Platts said. “Just quiet, kept to herself. We’ve been knowing her ever since she and her mother moved in about eight years ago. We’ve watched her grow up. This has shocked me.”

The family’s house, located in the 100-house North Crossing neighborhood, is within a mile of the Village at Sandhill mall. The neighborhood also backs up to the sprawling, mostly undeveloped Clemson Institute for Economic and Community Development campus off Clemson Road.

Sheriff’s investigators have combed the house for clues, canvassed the neighborhood, checked out nearby empty homes, talked to neighbors and Gabrielle’s friends and conducted phone searches and social media searches, Lott said.

Gabrielle’s purse and identification were still in the house. The only thing missing is her cellphone. There were no signs the Swainson house was broken into.

“Everything about this case concerns me,” Lott said.

Lott declined to talk about the cellphone that Swainson was believed to have with her. Modern cellphones contain technology that enables law enforcement to locate the devices.

Lott did say, “There is nothing to indicate that she voluntarily left home.”

The teen, who turned 15 in June, had just made Ridge View High’s junior-varsity cheerleading team, and she was excited to start her sophomore year of classes today, her mother told The State newspaper earlier this week.

Gabrielle has never run away, her mother said, and she didn’t think she had any reason to Saturday.

Theresa Riley, spokeswoman for the Richland 2 school district, said Wednesday school officials were keeping “close tabs on the situation. We will have counselors on hand for any students who may need that service.”

Riley said, “It’s a very sad thing, and we are just praying she is found very soon.”

For several days, Swainson’s friends, classmates and church have handed out fliers, started Twitter alerts (#FindGabby and #FindGabs) and set up a Facebook page, www.facebook.com/ findGabbiee.

Elvia Swainson has hired a private investigator, Chandra Cleveland-Jennings, who is a former member of the Richland County Sheriff’s Department. Elvia Swainson could not be reached Wednesday.

Many concerned friends met Tuesday afternoon at the Sandhill branch of the Richland County Public Library and canvassed surrounding neighborhoods, posting and handing out fliers bearing the missing teen’s photo and description.

Gabrielle is described as a black female, about 5-feet-2-inches-tall with black hair. She was last seen wearing pink and black pajamas.

The fact that school starts today underscores how serious Gabrielle’s disappearance is, said Tara Swainson, who was house-sitting the Tamara Way house Wednesday evening.

“Gabby’s a consistently A and B student. She loves to learn. Skipping school is not her thing,” said Tara Swainson.

“And her mom and her were thick as thieves – I just don’t see her doing this to her mom.”

Said Platts, the neighbor, “I’d hate to think somebody just come in and took her.”

Richland County sheriff’s deputies are asking anyone with information to call 911.

Reach Monk at (803) 771-8344.