Jon Jon Jackson's stunned and grieving mother is still trying to comprehend how her son could have drowned, according to The Post and Courier of Charleston.
"I'm still trying to wrap my mind around this," Cassandra Jackson told the newspaper. "It's really bizarre."
Jon Jon was autistic, but this played no role in his death.
Goose Creek police said Jackson swallowed some water while swimming around noon Sunday. Police said he later complained he was tired and took a nap. When someone checked on him, water was coming out of his nose and he was having trouble breathing.
The boy later died at Trident Hospital. Berkeley County Coroner Glenn Rhoad said the boy's lungs were filled with water and he died of asphyxiation. Rhoad said there was nothing suspicious about the death, and no way adults at the pool could have known what was happening.
The Post and Courier said so-called secondary drowning can occur up to 72 hours later and without any warning signs, according to medical experts.
Jon Jon's mother urged other parents to watch their children closely.
"Please check them when they get out of the pool. Just watch them like a hawk," she told the newspaper. "It tears me up inside. It's a heck of a sacrifice, but if this will help someone else, then it's all worth it."