CHRISTIANSBURG, Va. (AP) - The parents of a slain 13-year-old girl described their profound grief Tuesday, while teachers of the former Virginia Tech student convicted of stabbing her to death described him as a gentle person eager for acceptance.

The testimony came during a sentencing hearing for David Eisenhauer, who was an 18-year-old freshman engineering student at Virginia Tech when he developed a relationship with Nicole Lovell, a 7th-grader from Blacksburg.

In February, after days of damaging testimony at his trial, Eisenhauer pleaded no contest to first-degree murder, abduction and concealing a body in Lovell's 2016 death. He faces a sentence of up to life, plus 15 years.

As his sentencing hearing began Tuesday, Lovell's parents described the effect her killing has had on them.

Her father, David Lovell, said he's been diagnosed with severe depression and post-traumatic stress disorder since his daughter's death.

"There is nothing that will happen in this courtroom that will fix it," he said.

Lovell's mother, Tami Weeks-Dowdy, said she sees a grief counselor and still has trouble sleeping. She said she celebrated what would have been her daughter's 16th birthday last month at her gravesite.

Eisenhauer's lawyers called two teachers and a former classmate of his from Yakima, Washington, where he lived before moving to Columbia, Maryland, with his family.

Both teachers from the Riverside Christian School said he was a smart and kind student, but appeared to have trouble following social cues.

Kathryn Anne Stoothoff, who taught Eisenhauer in a 10th-grade English class and a bible class, said he was bright, but "needed clear rules to be successful." She said he would "follow someone off a cliff if they convinced him it was the right thing to do."

During his trial, prosecutor Mary Pettitt told the jury that Eisenhauer killed Lovell because he feared his relationship with her would be exposed. Pettitt said they had communicated online for months, then met in person.

Natalie Keepers, who prosecutors say was Eisenhauer's accomplice, told police Eisenhauer was worried the then-13-year-old Lovell could be pregnant. Keepers said Eisenhauer told her he may have had sex with Lovell at a party, but couldn't remember because he blacked out and later woke up in a ditch.

Keepers is scheduled to stand trial in September on charges of being an accessory before the fact and concealing a body.

Lovell's body was found just over the state line in North Carolina. A medical examiner testified that she had 14 stab wounds, including a lethal wound to her neck.

Copyright 2018 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.