Virginia Tech Student Had 'Inappropriate Relationship' With 13-Year-Old Murder Victim, Source Says

— -- The Virginia Tech student charged with kidnapping and murdering a 13-year-old girl is suspected of having a relationship with the victim that a source familiar with the probe characterizes as "inappropriate."

The source would not elaborate on the relationship to ABC News.

Police have given very little information about the nature of the relationship between the 18-year-old college student, David Eisenhauer, and the victim, Nicole Lovell, who was found dead after being reported missing from her room on Jan. 27.

Eisenhauer was arrested and charged with murder four days later. His attorney has not commented on the case.

"Based on the evidence collected to date, investigators have determined that Eisenhauer and Nicole were acquainted prior to her disappearance," the Blacksburg Police Department said in a statement released following his arrest. "Eisenhauer used this relationship to his advantage to abduct the 13-year-old and then kill her."

Eisenhauer's friend, Natalie Keepers, was also arrested in connection with the case. Prosecutors said Eisenhauer allegedly told investigators that he had been with Nicole on the night she disappeared.

Eisenhauer allegedly told investigators that he had seen Nicole climb out of her window on the night of her disappearance. But he left after giving her a "side hug," going back to the dorm of a close friend, later determined to be Keepers, Commonwealth prosecutor Mary Pettitt said in court on Thursday.

Investigators believe social media played a role in how Eisenhauer and Nicole communicated, and the app, Kik, released a statement saying that it was cooperating with the FBI in its investigation of the case.

Eisenhauer has been charged with kidnapping and first degree murder. Keepers was charged with being an accessory both before and after the fact as well as improper disposal of a body. Preliminary hearings have been scheduled for late March, but neither have had a chance to enter a plea yet.

Lawyers for both suspects have not made public statements regarding the cases.