The mother of 13-year-old Nicole Lovell, the Blacksburg, Va., girl who was kidnapped and murdered, broke down during a news conference held by investigators. (Reuters)

Two Virginia Tech students from the Washington area have been charged in connection with the abduction and slaying of a 13-year-old Blacksburg, Va., girl, who may have met one of the suspects online and who had been missing for four days before her body was found on the Virginia-North Carolina line.

Virginia Tech student David Eisenhauer, 18, of Columbia, Md., was arrested early Saturday at his dorm in Blacksburg and charged with abduction. Hours later, he was charged with first-degree murder after Virginia State Police located the remains of Nicole Madison Lovell on Route 89, in Surry County, N.C., along the Virginia line, Blacksburg police said.

Blacksburg police Lt. Mike Albert said that Eisenhauer abducted and killed the 13-year-old girl. Albert said that police determined that Eisenhauer knew her but declined to comment on the nature of their relationship.

Law enforcement officials on Sunday arrested a second Virginia Tech student in the case. Natalie Marie Keepers, 19, of Laurel, Md., was arrested on felony charges Sunday morning, alleging that she helped to dispose of the body, police said.

“Eisenhauer used this relationship to his advantage to abduct the 13-year-old and then kill her,” Albert said at a news conference in Blacksburg. “Keepers helped Eisenhauer dispose of Nicole’s body.”

Virginia Tech students David Eisenhauer, left, and Natalie Keepers were arrested in connection with the death of Nicole Madison Lovell. (Blacksburg Police Department via AP)

Police said Keepers, who was arrested off campus, was also charged with a misdemeanor for her alleged accessory role in the crime after the fact.

Eisenhauer and Keepers, both engineering students, are being held without bond at the Montgomery County, Va., jail.

Blacksburg Police Chief Anthony Wilson said the police investigation was swift.

“This has been an extremely fast investigation within the just past 12 hours,” Wilson said in a news release. “And we still have a great deal to do as there are multiple interviews to conduct and evidence” to collect and analyze “as we reconstruct the timeline of events leading up to Nicole’s tragic death.”

The girl’s body was transported to the office of the chief medical examiner in Roanoke for an autopsy, police said.

Virginia State Police spokeswoman Corinne Geller said divers Sunday were searching a pond on Virginia Tech’s campus for evidence in the case. Geller would not comment on what they were looking for.

The girl had been missing from her home since around midnight Wednesday. Her mother, Tammy Weeks, said a nightstand had been pushed up against the girl’s bedroom door and the window was ajar.

“She picked it up and put it against the door,” Weeks said. “The window was cracked when I went in.”

Nicole’s family had pleaded for the public’s help in finding her, because she needed daily medication after a liver transplant.

Weeks said police came to her home Saturday afternoon to tell her that her daughter’s body had been found.

“I’m shocked,” said Weeks, 43, a cashier at a local department store. “I’m hurt. It’s unbelievable.”

News of Nicole’s death spread late Saturday afternoon, shortly before an evening prayer vigil planned for her at the apartment complex where she lived.

Weeks said her daughter had survived a liver transplant, the staph bacterial infection MRSA and lymphoma when she was 5.

“God got her through all that, and she fought through all that, and he took her life,” she said. “That evil bastard took her life.”

Nicole, the youngest of four, was in seventh grade at Blacksburg Middle School, her mother said. Nicole had two brothers and one sister.

Nicole, who was born in Radford, Va., loved pandas and decorated her room with the stuffed bears and pillows covered with the “Minions” animated movie characters, her mother said. Her favorite color was blue.

“When she grew up, she wanted to be on ‘American Idol,’ ” Weeks said. “She loved to sing and dance. She loved anything to do with 5 Seconds of Summer. She loved country music, too — Elvis Presley, Conway Twitty. She liked Jason Aldean, Sam Hunt, all of them. I took her to a Brad Paisley concert when they had it at Tech.”

She said Nicole was bullied on social media and at school, particularly about her appearance.

“She was a typical student,” Weeks said. “She didn’t like going to school, because she was bullied. She was telling me that girls were saying she was fat and talking about her scars from her transplant.”

Nicole often cried, asking to stay home from school, her mother said. “We discussed it with teachers, but it got worse. It got so bad I wouldn’t send her.”

But the bullying, her mother said, continued on social media. “They can’t control those kids on social media,” Weeks said.

It was on social media where Nicole may have met Eisenhauer recently, Weeks said police told her. “That’s all I know,” she said. “It was some off-the-wall site I never heard of.”

Nicole wrote frequently on Facebook with romantic updates about her search for young love.

“First Kiss” she wrote on May 3, 2014.

“They say that Disney World is the ‘Happiest Place on Earth’. Obviously they’ve never been in your arms,” she posted on July 28, 2015.

On Jan. 1 at 3:35 a.m., Nicole posted a short message to a Facebook group called “Teen Dating and Flirting.” Captioned on a close-up selfie, the white flash of her cellphone camera illuminating her cheeks, she wrote: “Cute or nah.”

The message received 304 replies. Many of the comments were spiteful, not unlike the kind of bullying that is pervasive on social media.

“You’re very round,” one person wrote.

“And no not cute,” another commented.

On her Instagram account, Nicole wrote: “Its none of your business who I date.”

On Sunday, a commenter on the Facebook page of a group that calls itself Justice for Children Without Voices, which has been following Nicole’s disappearance, noted that one of the forums she had frequented was being shut down.

“ ‘Teen Dating and Flirting’ has been shut down! The page will take a full 24 hours to be removed. Many of you know this is one of the many groups and sites Nicole Lovell was a part of. Our children are in danger when exposed to this type of stuff online. We had personally began to reach out to parents of ‘real children’ in this group. We beg every parent here to please go through your child’s social media, pay attention who’s on their pages (FB, Instagram, KIK) to just name a few and let’s start protecting our children and teaching them right and wrong. It’s ok to be the ‘mean’ parent, they can thank us later.”

School officials would not comment on whether Nicole was bullied.

“When it comes to Nicole’s activities at school, the law precludes me from talking about that,” said Brenda Drake, public information officer for the Montgomery County, Va., schools system, which has 9,600 students and 20 schools. Drake said that Blacksburg schools will have additional grief counseling for students and teachers this week. “We have special places for students to go to sit and talk and share and memories of Nicole,” Drake said. We are doing everything we can to provide support for teachers, students and Nicole’s family.”

Drake said the school system has an anti-bullying program. “All teachers are trained to look for signs of bullying,” she said. “Students are encouraged to reach out and talk about bullying.”

Blacksburg police said that new developments in the case late Friday led to Eisenhauer and his arrest Saturday at his residence on campus.

The developments were unspecified, and it was also unknown what led searchers to Nicole’s body.

On Sunday, Eisenhauer’s dorm had been cleared of any reference to him, including his name tag, which had been removed from his door. Police officers roamed the halls. Eisenhauer’s name also had been removed from the university’s cross-country team’s online roster.

During high school, Eisenhauer was an elite athlete and track star. In 2014, while he was a junior at Wilde Lake High School in Howard County, Md., he won the Class 3A Maryland title for the 3,200-meter race.

At one point, he was named Athlete of the Week by a Baltimore television station and heralded as one of the top runners in the state and a stellar student.

Joe Keating, who was Eisenhauer’s co-captain on the Wilde Lake cross-country team, said members of the team were dismayed to hear the news of his arrest.

“We’re all just in utter shock,” Keating said. “We can’t get our heads around it.”

Eric Smart, who was also on the cross-country team, said the accusations against Eisenhauer were devastating. He said that his former teammate was focused on academics and his career. “I never saw any public signs of violence,” Smart said in a message.

Eisenhauer’s parents did not return phone calls seeking comment. No one answered the door at their home in Howard County.

Keepers was a 2015 graduate of Hammond High School in Howard County, a spokesman for the school system confirmed.

According to a Facebook page and LinkedIn profile believed to belong to Keepers, she wants to work in aerospace engineering after graduation. Her LinkedIn profile says she interned with NASA at the Goddard Space Flight Center in Greenbelt, Md., in 2014.

No one answered the door Sunday at Keepers’s parents’ home in Laurel.

A next-door neighbor said that Natalie Keepers was the oldest of four children. “There was nothing remotely remarkable about them,” said the neighbor, Lee Correll. “It’s your standard middle-class family.”

On Sunday, Weeks said that she was at the funeral home, making arrangements for Nicole. “We can’t believe this happened,” she said. “You never think it would happen to you.”

Nicole’s father, David Lovell, could not be reached Sunday, but he left a note on a Facebook page that had been created to support the search for his daughter.

On Saturday, Lovell wrote that he was devastated “to learn that my daughter has been found dead! I’m so in shock I know nothing more to say, I’m broken!”

A few hours later, he posted a photo of Nicole surrounded by a blue background, with the words, “In the arms of angels.”

Brown and Nirappil reported from Washington. Alice Crites, Julie Tate and Ashley Halsey III in Washington contributed to this report.