Fairfax County Police said Friday that they do not expect to file any criminal charges.
The boy had been hospitalized since the incident occurred Sunday at Pirate's Cove Waterpark in the Pohick Bay Regional Park.
Lifeguards cleared the pool around 5 p.m. due to lightning. At that point, the boy was discovered unresponsive at the bottom of the pool.
He was taken to Inova Fairfax Hospital and remained there until he was pronounced dead on Thursday. Police say the cause of death was drowning.
The waterpark is part of the Northern Virginia Regional Park Authority.
Related story: INVESTIGATORS: Drowning is silent