DURHAM — Durham police are counting on a 9-year-old boy to tell them who killed his 6-year-old sister and left him for dead. Investigators are still considering the possibility that the boy's father, Eric Crutchfield, pulled the trigger, then turned the gun on himself.

Detectives are talking to young Ricardo Crutchfield, who was shot twice by the assailant. Crutchfield is in fair condition at Duke University Medical Center. His father, Eric, is in serious condition at Durham Regional.

Police expect their interviews with the boy and his father to be just the breaks they need. Meanwhile, police say the investigation into the tragedy disturbs them.

"The tragedy is very draining on us, as well as on the public, when a child has been robbed of her opportunity to enjoy life," saysDurham PoliceCapt. Dwight Pettiford.

"Her brother was surely impacted for the rest of his life by that. He not only was shot, he lost his sister. Our sympathy goes out to the family," Pettiford says.

The children's mother, Pam Beasley, called 911 when she discovered her daughter, Brianna, and her son. The 911 call is considered key to solving this mystery. Police are not yet making the tape public.

Police recovered a small-caliber rifle at the scene, but they have not said whether the rifle they recovered is the weapon used in the shootings.

The children were apparently hit by some type of small-caliber round from a rifle or a handgun.

Crisis teams are atLittle River Elementary Schoolcounseling parents, teachers, and students.