ARAPAHOE COUNTY, Colo. A 5-year-old boy was killed in Arapahoe County this week and his 11-year-old brother is now under investigation for first-degree murder, deputies with the sheriffs office said Wednesday.Little is known at this time about what lead to the childs death, but Arapahoe County deputies said they responded to a home on South Jericho Street near the intersection with South Jericho Way in Centennial at around 5:30 p.m. Tuesday.Investigators said they later determined the suspect was the victims 11-year-old brother. The case is now being investigated as a homicide, according to a sheriffs office spokesperson.The child suspect who will not be identified because of his age was in custody at the Marvin W. Foote Youth Services in Centennial, the sheriff's office spokesperson said. 5-year-old boy killed by 11-year-old brother in Centennial, Arapahoe County deputies say"It is with great sadness that I want to share with you that one of our Kindergarten students has died unexpectedly," Timberline Elementary Principal Mary Bowens said in a letter to parents on Wednesday. "There is currently an active police investigation and law enforcement asked the District not to release the students name."Bowens said the district would offer additional district mental health staff "to support students and staff in processing this loss" on Friday. Other resources were available on the Cherry Creek School District's website.Our hearts go out to the family of these two young boys and to everyone in our community who is grieving this loss, said Sheriff Tyler Brown. Cases involving the homicide of children are among the most difficult our deputies and investigators face. Our team is fully committed to a thorough investigation, and we will continue working tirelessly to determine exactly what happened."The 5-year-old boys cause of death remains under investigation. ...read more read less