Sheriff's officials in Pasco County said the shooter used a handgun after the brothers had an argument about food in their home. The 16-year-old, who suffered a non-life-threatening injury, called police.
"This is a horrific scene," said Pasco County Sheriff Chris Nocco. "This is a nightmare."
The boys' mother and 18-year-old brother were not at home at the time of the shooting, officials said.
The shooter and victims' names were not provided, and police did not say how the boy obtained the gun.