KNOXVILLE, Tenn. (AP) — A former Division III college football player convicted of killing his ex-girlfriend says he never intended to cause her any physical harm.

William Riley Gaul apologized to 16-year-old Emma Walker's family Friday at his sentencing hearing, four months after jurors found him guilty of first-degree murder. The former Maryville (Tennessee) College wide receiver already is serving a life sentence with no possibility of parole for 51 years on the first-degree murder charge but now faces sentencing for lesser offenses connected to the case.

Gaul was an 18-year-old who had just finished his freshman season with Maryville when he shot through Walker's bedroom wall from outside her Knoxville home while she was sleeping on Nov. 21, 2016. Walker died of a gunshot wound to the back of her head, behind her left ear.

Gaul was dismissed from Maryville's team immediately after his arrest. He was convicted of first-degree murder on May 8.

"I know that nothing I can do will bring Emma back or alleviate the pain that I caused, but what I can do is tell the truth of what happened that night," Gaul said. "My intentions were not - and never have been - to cause Emma any physical harm."

Gaul, now 20, said he only meant to scare Walker into confiding in him so that he'd "be there to comfort her and win her back."

Defense lawyer Wesley Stone had made a similar argument during Gaul's trial. Stone said at the time that Gaul fired the shots in a misguided attempt at "coming to her rescue" and being Walker's "hero."

"Riley, you are not Emma's hero," Walker's mother, Jill Walker, said during the sentencing hearing. "You ended her life. No punishment will ever bring Emma back, but what helps is knowing that he can't do this to anyone else. Emma is the hero here, and she is definitely mine."

Walker's father and younger brother also spoke Friday while photographs of her appeared on the courtroom wall. Family friends spoke in support of Gaul.

Prosecutors said Gaul intended to kill his ex-girlfriend in anger over the end of their on-again, off-again relationship. Walker and Gaul had begun dating when both were at Central High School in Knoxville, where Gaul played football and Walker was a cheerleader.

"I'm sorry I took Emma away from you, that I robbed you of the experience of being able to watch your daughter grow up," Gaul said to Walker's family.

Gaul also apologized to his own family.

Jurors found Gaul guilty of felony murder, stalking, tampering with evidence, theft of between $500 and $1,000, and possession of a firearm in a dangerous felony as well as first-degree murder. Gaul also pleaded guilty before trial to reckless endangerment.

This sentencing hearing involved the lesser charges, since his first-degree murder conviction already carried an automatic life sentence. Knox County Criminal Court Judge Bob McGee set a Sept. 28 court date to discuss this case again before handing down a sentence on those charges.