A homeowner says his neighbor, 37-year-old Donald Hollman, threw the firework into his backyard then ran back to his home.
He says the firework exploded in the pool while his daughter and her three friends were swimming.
Fortunately no one was injured.
Investigators say Hollman was seen on security camera footage throwing the firework before running back to his house.
Police charged Hollman with child endangerment and unlawful possession of fireworks.
He's also facing weapons and drug charges after police found three shotguns and marijuana in his home.