A 15-year-old boy accused of fatally shooting his parents and three siblings in their wealthy Washington state home appeared in court Friday as investigators reveal chilling details about the killing spree.

The teenager has been charged with five counts of first-degree murder and one count of attempted murder in connection with Monday's rampage in the unincorporated community of Fall City, roughly 25 miles east of Seattle. His parents, Mark and Sarah Humiston, along with three of his siblings – ages 7, 9 and 13 – were found dead when deputies arrived.

Prosecutors on Friday sought a hearing to determine whether the teen suspect should be tried in adult court. A plea will not be entered until the hearing, which is scheduled for June 4.

Authorities allege the teenager used his father's gun that was stored in a lockbox. The suspected shooter was the only child in the home to know the code to the lockbox, according to court filings.

Court filings: 11-year-old sister survived by playing dead

Shortly before 5 a.m. Monday, the King County Sheriff’s Office received a 911 call from the suspect who said his brother had just “shot my whole family and committed suicide too," according to court filings. Investigators said the suspect shot his parents and siblings and then tampered with the scene so he could pin the blame on his brother.

The suspect's 11-year-old sister said she woke to the sound of gunshots and saw one of her brothers and her father lying in the hallway, the affidavit says. The girl said she witnessed the suspect shoot her sister.

The suspect then came into her bedroom and fired the gun, according to the affidavit, and she felt blood on her neck and hand. The girl stayed still and held her breath before she escaped through her bedroom window and ran to her neighbor's house, who called 911.

The 11-year-old said she recognized the weapon "as her father's silver Glock handgun," court filings say. She said her father kept the gun in a small lockbox occasionally kept near the front door so he could bring it to work.

When investigators asked her what issues the suspect had at home, she told them "he had recently gotten into 'a lot of trouble' for failing some tests at school."

Public defender Amy Parker said at the hearing Friday that community members have described the suspect as "kind and caring" who has many friends and has been "a positive contributor to his community."

"Given the media interest in this case and the seriousness of these charges, we want the court to know that multiple people in the community have reached out to us who know our client, and they have attested to his good character," Parker said.

A next court date is scheduled for Jan. 8.

Tragedy brought Fall City together in mourning

Fall City is mourning the deaths of four community members after the quintuple shooting shocked the small town of roughly 2,000 residents. Pastor Carrie Bland said it was heartwarming to see people come together.

“It's been amazing to see how the town has jumped to come together to support everyone even if they didn't know each other,” she said. “They're doing it to make sure that everyone is taken care of.”

Several churches in the area are helping families grieve. Bland said the Snoqualmie Valley Alliance Church is hosting a grief and information session with the King County Sheriff’s Office for locals. There, she expects people to learn a bit more about what happened and what mental health resources are available.

Bland is also changing up her church’s Nov. 3 open house to focus Sunday service on grief and loss, and mental health resources will be made available. Beyond that, Bland said the holidays are approaching and the shooting may alter how families celebrate. No matter what, she hopes people use it to spend more time together.

“A lot of families are going to be grateful and thankful for the families who are around the community,” she said.

Laws target unsecured guns in homes

The shooting in Washington highlights the prevalence of unfettered access to guns that are used in killings across the United States, said Jennifer Dolan-Waldman, vice chair of Seattle-based Grandmothers Against Gun Violence.

Gun violence is the leading cause of death for children in the nation, and authorities have prosecuted parents for provided access to weapons in recent high-profile cases, including mass school shootings in Georgia and Michigan.

“The bottom line is kids should not have guns,” Dolan-Waldman told USA TODAY.

This week also marks the tenth anniversary of the mass shooting at Marysville-Pilchuck High School, about 60 miles north from the family’s home, in which authorities said a 15-year-old student used his father’s gun to kill four people and injure one before fatally shooting himself. The father was later convicted of illegal firearms possession.

Just last month, the father of the suspected shooter at Apalachee High School in Georgia was charged with involuntary manslaughter, second-degree murder and cruelty to children for allowing his son to possess a weapon. In Michigan, parents of a mass school shooter for the first time were convicted of involuntary manslaughter for the four deaths at Oxford High School.

Everytown ranks Washington’s gun laws ninth in the nation, and their gun deaths rate of 12 per 100,000 residents is slightly lower than the national average – but it is still well above the global rate of about 3 deaths. The patchwork of state laws also means that guns can be bought in one part of the country and cross state lines.