Colton Harvey, 15, pleaded guilty on Wednesday to murdering his older sister while she slept in Arkansas. He was sentenced to 45 years in prison for a crime in which there appears to be no motive.

In the early morning January 15, Harvey grabbed his father's .22 caliber-rifle while his mother and father went grocery shopping. He casually walked into his sister's room and placed the end of the gun to her head. Candace Harvey was startled and woke up with a terrifying scream. Harvey then pulled the trigger, shooting her in the head a total of three times, reported the Associated Press.

Prosecutors said Harvey then tried to flee. He grabbed clothes, ammunition and stole his father's pickup truck. He into the local hills, but changed his mind and drove to the sheriff's office. He left the sheriff's office and then stopped by a friend's house, only to return and confess to his brutal crime, the AP reported.

I don't know why I did it. It just happened, Harvey told state police investigator Corey Mendenhall.

Investigators still found Candace's body in her bedroom at the family's home near Ozark, Ark.

During the investigation, the sheriff of Ozark, Anthony Boen, said Harvey seemed remorseful and was in tears when he turned himself in, CBS reported.

Harvey also told Mendenhall that he deserved to be shot.

I should get done to me what I did to her, Harvey said.

The morning Candace was killed, Harvey's parents woke him up to begin preparing a deer he killed the weekend before.

You've got to be angry to be able to shoot a gun at somebody, Mendenhall, the state police investigator, told him a few hours after Harvey murdered his sister. I mean, you're used to shooting deer and stuff and I know you're, you're not angry at the deer. But we're talking about your sister here. Do you love your sister?

Harvey said he did.

Prosecutors charged the teen with first-degree murder, seeking the maximum penalty of life behind bars without the possibility of parole. However, they worked out a plea deal with his defense attorney, William O. Bill James. On Wednesday, the judge presiding over the trial handed down Harvey's sentence. He will serve 30 years for second degree murder and 15 more years for using a gun.

 You stated that you murdered your sister. Is that correct? Judge William Pearson asked. Harvey gave a quiet response and said Yes, sir.

How far did you get in school? Pearson asked Harvey. He told the judge he only got as far as the ninth grade as his mother began to cry.

However, there was no definitive motive for the murder.

He never did give what I would consider to be a clear motive, prosecutor David Gibbons said after the sentencing hearing, reported CBS.

His parents said they never fought, reported 5 News.

Harvey's attorney said that the family has a history of mental illness, but an expert was unable to diagnosis his client because he was only a teenager.

Every time I've ever seen him, he's cried, James said. And it's not, 'Woe is me.' It's about what he's done to his mom and what he's done to his family.

The state reviewed Harvey's mental health after it was reported he became very depressed while sitting in his cell.

Until Harvey turns 16, he will be held at the state's Division of Youth Services. Then, he will be transferred to the Arkansas Department of Corrections, reported 5 News.