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A 15-year-old girl and her 11-year-old sister have been arrested in Florida and charged with the murder of their 16-year-old brother, authorities said Tuesday.

The Columbia County Sheriff’s Office said that the 15-year-old, grabbed a handgun from her parents’ bedroom and fatally shot her brother, 16, sometime before 10 p.m. Monday in the living room of their home, and that the 11-year-old helped in the crime.

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The older girl was arrested and charged Monday, and her 11-year-old sister was arrested Tuesday afternoon, the sheriff’s office said. Both are charged with premeditated murder.

Officials learned of the killing after a police officer in nearby White Springs ran into the two girls, who told the officer that there had been a shooting at their home. Columbia County sheriff's spokesman Deputy Murray Smith said 15-year-old told the officer that her brother had beaten her up earlier in the day, and investigators believe that prompted the fatal shooting.

It is unclear how the 11-year-old was involved, but the sheriff’s office said in a statement Tuesday that she allegedly "assisted" in the killing. The name of the slain 16-year-old was not released.

The children’s parents, aged 37 and 33, were out of town at the time, but were later arrested on charges of child neglect for failing to supervise their children. Another 3-year-old at the home was taken into custody by the state Department of Children and Families, the sheriff’s office said. Both parents remained at the Columbia County Detention Facility on no bond, according to jail records.

No one answered the phone at their home. White Springs is located in the northern part of the state, about 20 miles south of the Georgia border.

— Phil Helsel

Editor's note: An earlier version of this story named the girls and their family and included their pictures before it was learned that they may have been the victims of sexual abuse.