(CNN) -- Prosecutors are expected to file formal charges Friday against a 12-year-old Colorado boy suspected in the deaths of his parents and the critical wounding of two siblings.
The boy, whose name has not been released, appeared in court in Fort Morgan Wednesday night in a closed hearing. The judge advised the youth of his rights and ordered him held without bond until his next court appearance, said District Attorney Bob Watson of the 13th Judicial District.
The next appearance is to be in Burlington, where the shooting occurred, on March 14.
Burlington, a town of fewer than 4,000 residents, is located near the Colorado-Kansas border.
The boy called 911 on Tuesday to report that at least three people in his house had been shot, police said.
Upon arrival, officers discovered the bodies of the boy's parents, both in their early 50s.
Officers also found two critically wounded children: a 5-year-old girl and a 9-year-old boy, whom authorities identified as siblings of the boy in custody.
The children were taken to an area hospital and then transferred to a facility in Denver.
Authorities have released few details about the investigation. A judge has issued a gag order and sealed the records in the case, including warrants, affidavits and the 911 recording. A coroner's report on the cause of death is pending.
Colorado law dictates that charges must be filed initially in juvenile court because of the boy's youth. However, the law does permit the district attorney to request that the case be moved to district court.
CNN's Melanie Whitley and John Branch contributed to this report