In a heart-wrenching development in Colorado, parents are grappling with an unimaginable tragedy: their 11-year-old son stands accused of murdering his 5-year-old brother. The incident has shocked the Centennial community, where the siblings were well-known for their friendly visits to neighbors’ homes, often seeking snacks and greetings.

“He was always with him,” a neighbor told local NBC affiliate KUSA, describing the victim Elias Reliford and his brother, who has not been identified, as “very playful and very nice.”

Residents of the area recall the deep bond shared by the brothers, with Elias, the younger sibling, constantly in tow with his older brother. “His older brother was always there, never leaving him alone,” a neighbor shared with KUSA, emphasizing the boys’ eagerness to engage with those around them.

The Arapahoe County Sheriff’s Office, in conjunction with the 18th Judicial District Attorney’s Office, announced the arrest of the older brother on March 11. He faces charges of first-degree murder and an aggravated juvenile offender enhancement. Currently, he is being held at the Marvin W. Foote Youth Services Center in Centennial, officials confirmed to Law&Crime.

As the family mourns, tributes have flooded social media, painting a picture of Elias as an extraordinary child with roots in Louisiana. His uncle expressed his sorrow on Facebook, writing, “My heart is broken and my feelings are shattered.” He fondly remembered Elias as “my Baby mane forever and ever,” adding, “I love you, Nephew, gone miss you.”

Facebook posts have poured in from the children’s family and friends, describing Elias as an “extraordinary” child with ties to Louisiana.

“Man my heart is broken and my feelings are shattered,” wrote Elias’ uncle in a March 16 Facebook post. “This was my Baby mane forever and ever,” he said. “I love You Nephew gone miss you.”

Photos posted by family and local ABC affiliate KMGH show Elias smiling and laughing with loved ones, including a video his dad posted on March 14 of them singing the Benson Boone song “Beautiful Things” together.

“This lil dude,” wrote the boy’s father.

The coroner’s office told Law&Crime on Wednesday that Elias’ cause of death “is pending the final autopsy report” and is still under investigation. “The pathologist has not determined anything yet,” a spokesperson said.

Authorities responded to the family’s home in the 5200 block of South Jericho Way at 5:30 p.m. that Tuesday and found Elias dead. Details of how he was discovered have not been released. Arapahoe County Sheriff’s spokesman Anders Nelson told The Denver Post that the investigation was “very complex.” Sheriff Tyler Brown has called it “one of the most difficult” cases his office has ever faced, KMGH reports.

“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 in a statement.

“It’s something that, literally as a parent, is probably your worst nightmare,” a neighbor told local CBS affiliate KCNC.

Elias’ brother is being charged in juvenile court. Elias is scheduled to be laid to rest on Friday in Shreveport, Louisiana.