No one disputed he fired the shot that killed Emma Jane Walker.

The question for jurors was whether William Riley Gaul pulled the trigger with the intent to kill his 16-year-old cheerleader ex-girlfriend.

After deliberating for four hours Tuesday, a jury said yes, he did, and convicted Gaul, 19, of first-degree murder. He stole his grandfather's gun and used it to shoot Walker through her bedroom wall as she slept in the Sterchi Hills subdivision of North Knox County on Nov. 21, 2016.

Jurors also found Gaul guilty of stalking, felony murder, tampering with evidence, reckless endangerment, possessing a firearm during a dangerous felony and theft between $500 and $1,000.

Criminal Court Judge Bob McGee imposed a mandatory life sentence for the murder charge. Gaul's bond was revoked, and he was taken into custody.

Gaul will be eligible for parole after serving 51 years in prison. He would be in his 70s.

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From texts to gunshots

During closing arguments Tuesday, Gaul's defense attorney, Wesley Stone, argued his actions were reckless but not murderous.

"This case is about state of mind," Stone told the jury. "Riley did not mean to hurt her or cause her death. He was trying to get her attention. I'm not saying it's logical."

Stone asked the jury to find Gaul, a former Maryville College football player, guilty of reckless homicide — not first-degree murder — for shooting the Central High School cheerleader through her bedroom wall.

Jurors made their decision without hearing from Gaul in person. He chose not to testify.

Prosecutors said Gaul became obsessed with Walker and wouldn't take no for an answer when she tried to end their relationship. He and Walker had been texting and calling up until the morning of her death, when two gunshots penetrated her bedroom. One of the bullets struck Walker just behind the ear, killing her. Crime scene evidence suggested she died instantly.

"He was possessive, manipulative, controlling," said Kevin Allen, a Knox County assistant district attorney general. "He was toxic to her. This was no accident. This is about criminal intent to kill."

Gaul and his lawyer admitted he fired the gunshots — not to kill Walker but to scare her and send her running back into his arms. He'd already made other outlandish bids for attention that weekend, including sending Walker anonymous, threatening texts and staging suicide attempts and his own kidnapping.

"My client was her hero," Stone told the jury. "As crazy and bizarre as it sounds, he was hoping to come to her rescue."

The bullets came from a 9mm Glock stolen by Gaul from his grandfather's vehicle. Testimony showed Gaul recruited friends to help him ditch the gun after the shooting, but they had already gone to authorities.

Gaul's friends secretly recorded him at the behest of Knox County Sheriff's Office investigators, and he was arrested just as he prepared to toss a trash bag of evidence, including the gun, into the Tennessee River.

Prosecutors pointed out Gaul told one lie after another from the morning of Walker's death. He denied he took the gun, lied to detectives, asked his friends to lie for him and claimed he'd been in Maryville even though data recovered from his cellphone showed he'd been near Walker's home when the fatal shot was fired around 3:45 a.m.

"He can't even kept his alibi straight," Allen said.

Gaul's lawyer said he didn't think the gunshots would penetrate the walls of the bedroom and put Walker in real danger. But Gaul had been in the bedroom, knew where Walker slept and had even shot photos and video there. Investigators concluded the gunshots had been fired from as close as 4 or 5 feet from the bedroom window.

"You wouldn't have to spend 10 seconds in that room to know where Emma slept at night and where her head would be," Allen said.

"His story doesn't make sense because it isn't true."