A college football player who allegedly shot dead his 16-year-old cheerleader girlfriend as she slept tweeted about how much he loved her hours before he was arrested.

William Riley Gaul, 18, was charged with murder on Wednesday after Emma Walker was found dead inside her home in Knoxville, Tennessee.

The Maryville College football player is accused of firing a gun into Walker's bedroom from outside her house while she was sleeping on Monday morning.

The couple had recently ended their relationship but Gaul refused to accept the breakup, according to Walker's aunt Jenny Weldon.

William Riley Gaul, 18, has been charged with the murder of 16-year-old cheerleader Emma Walker after she was found shot dead in her bed in Knoxville, Tennessee on Monday

Video courtesy WATE

'She had chosen to move on,' Weldon told the Knoxville News Sentinel. 'He refused to accept it. He chose not to accept her wishes.'

Gaul, who was arrested on Tuesday night, had been under surveillance by Knox County Sheriff's Office detectives because they believed he was preparing to destroy evidence related to the homicide.

The pair had both been students at Central High School before Gaul graduated this year.

Just prior to his arrest late on Tuesday, Gaul posted a lengthy tribute on Twitter professing his love for Walker and reminiscing about conversations the young couple had about planning their future family.

'To think that every memory we have, every happy special moment we shared, can't ever be relived. I love you Emma Jane Walker,' Gaul wrote.

The body of cheerleader Emma Walker, 16, was found in her bed at her home in Knoxville, Tennessee on Monday morning with a gunshot wound

Gaul was charged with Walker's murder on Wednesday. He is accused of firing a gun into the teenager's bedroom from outside her house while she was sleeping

The Maryville College football player posted a lengthy tribute on Twitter professing his love for Walker hours before his arrest for her murder on Tuesday night

'The amount of pain your family, me, the community are in because of this is insurmountable. Every time we held hands, kissed, hugged, to imagine that I'll never have that ever again hasn't quite yet hit me yet.

'I'll never forget those times we talked about our future and what kind of dog we'd get and how awesome our family would be. I'll never forget sitting on the couch, watching Dr. Pimple Popper and making popcorn and laughing and holding you.

'You're beautiful, you're amazing, you're funny, compassionate, caring... you're my best friend. There's not a human on earth that can make the impact that you've had on my life. I miss you more than anything.

'Just knowing you have someone that's so in love with you gives you so much hope for your life ahead, and it can be taken away, just like that.'

Police say Gaul fired a gun into Walker's bedroom from outside her house in Knoxville (pictured) while she was sleeping on Monday morning

Walker was a student and cheerleader at Central High School where Gaul also attended prior to his graduation this year

Gaul said in his lengthy tribute that it was surreal to think the girl that made his 'world spin' and gave him reason to wake up every morning was gone

Gaul posted this tweet on Tuesday while Walker's family and friends gathered at a memorial service for the teenager at Central High School. He was arrested just hours later

Gaul took to social media to post a loving tribute to Walker a day before he was arrested over her murder

Gaul's social media profiles are filled with photos of the pair and references to the slain cheerleader.

Walker's family and friends gathered at a memorial service for the teenager at Central High School on Tuesday night.

At the time of the memorial, Gaul tweeted: 'I love you Emma, I can't be around any of that yet, it's too soon. I know you know I'm dying to be there but understand I can't. I love you.'

He is listed on the Maryville Scots football team's website as a freshman wide receiver. He most recently played on November 12 against Greensboro in North Carolina.

Gaul is being held on a $750,000 bond in the Knox County Jail.

He will face court within the coming days on his first degree murder charge.

Gaul posted this lengthy tribute on Twitter to his slain girlfriend just hours before he was arrested for her murder