Shock reverberated through a quiet neighborhood in Centennial on Thursday, a day after authorities said they arrested an 11-year-old boy under suspicion of killing his 5-year-old brother.

Neighbors described the area as a close-knit, quiet community.

“It’s the type of neighborhood when someone goes out of town, others feed their pets and water their plants,” neighbor Mona said, who declined to provide her last name. “Kids play together in the summer.”

She said she has never witnessed anything like it.

“It’s a quiet neighborhood,” she said. “I’ve never seen a police response like this.”

Few details emerged a day after Arapahoe County Sheriff’s Office deputies arrested the 11-year-old boy on suspicion of first-degree murder. The officers had responded on Tuesday and soon after disclosed that the older brother is the suspect.

“The case is being investigated as a homicide. The cause of death remains under investigation,” the authorities said on X.

The Denver Gazette requested the release of any recording of the 911 call, but a spokesperson for the sheriff’s office said the case remains sealed while it’s under investigation.

In the wake of the death of a 5-year-old student, Cherry Creek School District is providing mental health support to staff and students, officials said.

“It is with great sadness that I want to share with you that one of our kindergarten students has died unexpectedly,” Timberline Elementary School Principal Mary Bowens wrote Wednesday in a letter to parents. “There is currently an active police investigation and law enforcement asked the district not to release the student’s name. We ask the community to honor the family’s privacy at this time.”

Ashley Verville, a Cherry Creek School District spokesperson, said that mental health support is being provided and will be “for the foreseeable future.”

While it is unclear how many mental health professionals are assigned or were deployed to the school, Abbe Smith, a district spokesperson, said every campus has “school psychologists and school social workers, to provide ongoing support for students.”

The district did not disclose whether the incident affected attendance Thursday.

“When a school community experiences a tragedy such as the loss of a student, the district immediately activates its crisis response protocols,” Smith said. “This includes convening our mental health leadership team and deploying crisis prevention and intervention staff to the school to provide care, counseling, and support for students.”

The district’s Employee Assistance Program is offering in-person and telehealth appointments at no cost, Smith said.

“Our focus in these moments is ensuring that students and staff have access to the care and resources they need during an incredibly difficult time,” Smith added.

Located in Centennial, Timberline Elementary School is a public pre-K to 5th-grade school with roughly 450 students.

In an earlier statement, Sheriff Tyler Brown said he anticipates an emotionally-wrought case.

“Our hearts go out to the family of these two young boys and to everyone in our community who is grieving this loss,” Brown said. “Cases involving the homicide of children are among the most difficult our deputies and investigators face.”

Meanwhile, former Arapahoe County felony prosecutor Eric Faddis offered several insights into the law when it comes to charging juveniles with premeditated murder.

While the 18th Judicial District Attorney has not yet filed charges in the case, and did not indicate that the juvenile would be charged as an adult, Faddis talked about the circumstances in which they would.

“Prosecutors consider a number of factors when deciding whether to try and charge a minor in adult court,” Faddis said. “Those factors include the seriousness of the alleged offense, whether the juvenile has any criminal history. They also take into account the juvenile’s maturity, the community interest in punishing the alleged act, as well as the impact on the victim, and in this case, the decedent’s family, of which the defendant is a member.”

Colorado law prevents moving a juvenile case to adult court for anyone younger than 12 years old. The process is called “direct file.”

Faddis said he didn’t recall the 18th Judicial District ever direct filing against a juvenile in his time there.

The longest sentence a juvenile can get, for any offense conviction, is seven years, he said.

“I think some folks have talked about reconsidering those sentencing limitations for juveniles, as we see a greater frequency of alleged juvenile crimes being committed,” Faddis said.

He added: “If he were to receive the maximum sentence of seven years, he would likely be out once he became an adult at 18.”

Denver Gazette reporter Nicholas Fogleman and City Editor Dennis Huspeni contributed to this report.