EVERETT — An Everett teen will face the adult legal system after allegedly admitting that he killed the woman who for more than a decade had provided him with a home.

Brad George, 16, was ordered jailed in lieu of $500,000 cash-only bail during a brief hearing Monday in the juvenile division of Snohomish County Superior Court.

He was being held for investigation of first-degree murder in the killing Friday of Gina Latshaw, 37, his legal guardian and also the woman he called “Mom.”

In keeping with state law, the seriousness of the allegation requires George’s case to be handled in the adult legal system, prosecutors said.

Police suspect that the killing was premeditated, and that George took a number of steps to try to hide his involvement. The teen also has a long history of mental health issues.

It was George who phoned 911 on Friday afternoon, summoning police to the apartment on Fifth Avenue W. in south Everett where he and Latshaw lived. He reported coming home from school, and being concerned because the apartment door was ajar and Latshaw’s car was outside. She normally would have been at work.

Officers found her inside with apparent blunt-force trauma to the head, according to a police report filed in connection with Monday’s hearing.

Detectives were summoned. In a nearby garbage can they found a purple plastic dumbbell and clothing. The items appeared stained by blood.

There were no signs of forced entry in the apartment. Money was reported lying out in plain sight.

The apartment was searched with a judge’s permission. An apparent match to the purple dumbbell reportedly was found in George’s room.

Detectives interviewed Latshaw’s family and friends, and they reported that the teen had threatened her before, including once with a knife, the police report said.

George reportedly had been having behavior issues related to medication he’s been taking to help him control a variety of challenges, including mood and conduct disorders and post-traumatic stress, the police report said.

He told detectives that he’d stopped taking his medications about a week earlier.

When asked whether he’d hurt Latshaw, George initially denied involvement, according to police. He reportedly was nervous and shaking when questioned about the dumbbell found in his room, and told investigators that it was a gift from a neighbor, and that he had been given only one.

He was arrested on Saturday evening for investigation of second-degree murder. On Sunday, he was again questioned by police and reportedly admitted killing Latshaw, the report said.

Prosecutors have asked that George be held for investigation of first-degree murder. On Monday morning they began the process of moving the case into adult court.

Latshaw won legal custody of George when he was 5 years old. In court papers, she argued that the boy and his then 11-year-old sister needed a stable home. His father was in prison at the time. Court records show the man has 12 felony convictions, half for possessing methamphetamine. In 2013, he was sentenced to two years in prison for heroin possession.

Latshaw listed her job as an IT project manager for a local aviation company on a social media site. Between 2005 and 2007, she worked for the city of Everett parks department while attending college classes, according to city records.

All the while, she was trying to care for a child with a history of behavioral issues.

Everett police have had contact with George in the past. In 2010, when he was 12, he ran away for several days and police sought the public’s help in tracking him down. Latshaw was interviewed for the article, and spoke of having raised the boy since he was 17 months old.

At about same time, George was treated at a local hospital for mental health issues and threats of violence, according to police.

At the time, he reported having “extreme hallucinations envisioning his mother as a short clown with a blood-filled mouth,” the police report said. He also reportedly made a clay sculpture of her with a severed head.

During an evaluation interview, he reportedly became non-responsive and pulled a wooden arm from a chair and started tapping it in the palm of his hand. He then allegedly started walking toward the nurse and raised the piece of wood as if to strike her. He was disarmed by security guards after the nurse screamed. At the time, he was diagnosed as having homicidal thoughts.

In 2011, George again was the focus of news reports after he ran away from a Seattle center that cares for patients facing mental health issues. He was 13.

Prior to his arrest on Saturday night, George was interviewed by Seattle television stations about Latshaw’s death.

During an interview with detectives on Sunday, George reportedly said that he stopped taking his medications Feb. 1 and had not slept for three days.

He said he got up late Thursday night or early Friday morning after Latshaw had gone to bed. He tried to clear his mind of negative thoughts, but reportedly was convinced Latshaw was poisoning him with bleach.

He grabbed the dumbbell and went to her bedroom, he told detectives.

When he tried to open the door, he realized that Latshaw had locked it and had recently installed a security bar.

George reportedly told detectives that he retrieved a coat hanger from his room, slipped it under the door and was able to disable the security bar. The teen allegedly said he waited for about five minutes to make sure Latshaw was still asleep, then entered the room, stood over her for roughly 15 seconds and then struck her more than three times with the dumbbell.

After cleaning himself up, he said he dumped his clothes, the dumbbell and cleaning supplies in a neighbor’s garbage. He then said he staged the home to look like a burglary, throwing away Latshaw’s purse and cellphones in a convenience store dumpster. He also threw a signed baseball and camera into some brambles on some neighboring property. Then he went to school.

Police said they recovered many of those items in the locations where George said he’d left them.

Eric Stevick: 425-339-3446, stevick@heraldnet.com.