[ UPDATE: Arrest made in connection with fatal accidental shooting of Jacksonville 5-year-old girl ]
ACTION NEWS JAX INVESTIGATES: What would your child do if they discover a gun?
Police said three Jacksonville children were home alone when an 8-year-old boy found a gun inside an apartment and accidentally fired it, killing his 5-year-old sister and injuring a 4-year-old neighbor.
Police said the 8-year-old and 4-year-old ran next door and told a neighbor Serenity Allen had been shot.
The 8-year-old found the gun inside an apartment at Roosevelt Gardens, police said.
Photos: Girl killed, brother hurt in accidental shooting at Jacksonville apartment
The 4-year-old boy's injuries are not considered life-threatening, police said.
The three children were alone inside the apartment, according to Jacksonville Sheriff's Office.
Officers said the mother of the Serenity and the 8-year-old may have gone to the store. They are investigating where the gun was and how the 8-year-old got access to it.
The Florida Department of Children and Families is investigating what led to the shooting.
“It comes down to responsible gun ownership, and securing your weapons within your home, making sure they’re locked up and making sure children don’t have access to them," Chief Chris Butler with Jacksonville Sheriffs Office said.