Two Virginia Tech University engineering students appeared in court Monday in the death of a 13-year-old girl whose body was found four days after she apparently climbed out her bedroom window. Police released no more details.

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WHAT WE KNOW:

— The victim: Nicole Madison Lovell, 13, was a seventh-grader at Blacksburg Middle School who overcame a liver transplant and other health problems, but suffered from bullying at school and online, her mother said.

— The suspects: David Eisenhauer, 18, is charged with kidnapping and first-degree murder. Natalie Keepers, 19, is charged with improper disposal of a body and accessory after the fact in the commission of a felony. Both are jailed without bond, and told a judge they have lawyers. Neither had a prior criminal record.

— The timeline: Nicole's family discovered Wednesday that she apparently climbed out her bedroom window overnight. Her body was found Saturday just across the Virginia state line in North Carolina, hours after Eisenhauer was arrested.

WHAT WE DON'T KNOW:

— The circumstances: Police have not released any information about what happened to Nicole between the time she left home and when her body was found.

— The means: Authorities have not said how she was killed. According to the arrest warrants, no firearm was used.

— The motive: Authorities have not said why Eisenhauer would have committed first-degree murder.

— The clues: Police said Eisenhauer was acquainted with the girl, but did not provide any details, including what led officers to him.

— The evidence: Police divers have been searching a pond on the campus; a spokeswoman would not say what for.