A mistrial has been declared in the case of a Marysville officer charged with manslaughter after his 3-year-old son fatally shot his 7-year-old sister with an unsecured gun.

Derek Carlile is accused of leaving a loaded .38-caliber revolver in a cubbyhole in the family van, then getting out and leaving his four young children inside. Investigators say the 3-year-old grabbed the gun and fatally shot his older sister.

On Tuesday, the jury was declared hung.

Prosecutor Lisa Paul says "no reasonable person would leave a loaded unsecured gun in a van with four children."

Defense lawyer David Allen told the jury that the shooting tragic mistake.

Carlile will be retried in January.