SANTA CRUZ (CBS SF) — A 15-year-old boy has been charged as an adult in the death of 8-year-old Madyson “Maddy” Middleton in Santa Cruz earlier this week.

Adrian Jerry Gonzalez was charged with murder, kidnapping and sexual assault, Rosell said during a news conference outside the Santa Cruz County Courthouse Wednesday morning.

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The murder charge includes special circumstances involving sexual assault, kidnapping and lying in wait, Rosell said.

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As for the motive, Rosell said, “I can tell you this. People do things for lots of reasons. Sometimes we understand them, sometimes we don’t.”

Gonzalez is being held at the Santa Cruz juvenile detention center and scheduled to be arraigned on Thursday.

The death penalty is not applicable to juveniles and the teen is facing life in prison if convicted on the charges, according to Rosell.

As for charging Gonzalez as an adult, Rosell said he did not take it lightly.

“You look at the nature of the crimes, look at how the crimes were committed, you look at the age of the offender, and you look at criminal record if any,” he said. “Is it typically the factors used to balance.”

Instagram users have known for days Gonzales was the suspect.

He posted a video on Sunday, the same day Maddy was killed.

In it, he’s playing a song on piano called “Mad World” and posted the lyrics, “the dreams in which I’m dying are the best I’ve ever had”.

Gonzalez and Maddy were acquaintances and neighbors who lived at a housing complex at the Tannery Arts Center campus at 1030 River St., police Chief Kevin Vogel said.

“She was lured to the suspect’s apartment willingly,” Vogel said. “We determined she was murdered inside the apartment. She was then carried downstairs and put in the recycle bin.”

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A detective found the girl’s body inside a recycle bin on the first floor of the Tannery Arts Center, around 5 p.m. Monday.

The girl was first reported missing on Sunday, at 6:08 p.m. Police now believe she had already died by then.

“It is my belief she was killed even before we got the phone call on Sunday night,” said Vogel.

Police said after the suspect was taken into custody, he was interviewed for several hours and subsequently arrested.

Vogel said a search of Gonzalez’ apartment has turned up evidence that linked him to the crime.

“She knew him, she had a reasonable amount of trust,” he said. “We don’t believe she was taken there against her will.”

Maddy was set to enter fourth grade next month at DeLaveaga Elementary School, Santa Cruz City Schools district superintendent Kris Munro said.

“We are stunned and deeply saddened in the wake of the tragic news about Maddy Middleton,” Munro said in a statement on the district’s website.

“Our hearts go out to her family, friends, and loved ones, many of whom are members of our school community as well as our larger community,” Munro said.

The district is offering counseling services today and Thursday at the school for students, families and staff, Munro said. The times for the counseling services and resources to cope with Maddy’s passing are posted on the district’s website at http://www.sccs.santacruz.k12.ca.us.

A memorial has also been set up in Maddy’s honor, overflowing with dozens of bouquets, stuffed animals, balloons, candles and notes.

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