Law enforcement sources said the police discovered the body of the 21-year-old man on early Sunday at the bottom of the pool after he apparently drowned, reported TMZ.
Moore's caretaker threw a party and invited the victim while the 52-year-old "Very Good Girls" actress was out of town.
The caretaker and others allegedly went out at some point leaving the victim behind and when they came back the victim was already at the bottom of the pool.
Sources said the victim, who didn't know how to swim, apparently slipped and fell in the pool.
There was no foul play and police are still investigating the case. Moore's representative hasn't commented on the issue yet.