The incident happened around 4:30pm at the Chimney Rock apartments in the 5400 block of Chimney Rock.
A witness says the boy was swimming under his grandmother's watch when something went wrong.
The witness says the boy was found at the bottom of the pool, and a neighbor jumped in, pulled the boy out and started administering CPR.
"He's going to be OK. I'm just here thinking about it, thanking God for it right now," the witness told us. "Parents need to watch their kids more often at the pool. I know it's hard and everything but pay attention."
The boy was taken to Texas Children's Hospital. The neighbor who administered CPR at the scene says the boy did have a pulse as he was being transported to the hospital. However, authorities could not confirm his condition.
Detectives are still trying to figure out exactly how the boy ended up in the bottom of the pool.