Michael "Mickey" Tylo Jr. was pronounced dead at 11:55 p.m. Thursday, TMZ.com reported Friday.
"It has already been determined that this was an accident," Clark County Coroner Michael Murphy told People. "Looking at the report, it appears that he fell in the pool after having some sort of medical event. It says on the report that he had a seizure disorder."
The drowning occurred at a residence and was discovered by an unidentified family member, Murphy said.
"We are doing a toxicology report, but that is standard with all bodies that come to us," added Murphy. "That information won't be available for several weeks. With this already having a cause of death, like a medical condition, it appears pretty evident that this is reason for him falling in the pool."
A representative for "The Bold and the Beautiful" told the magazine: "Hunter is not commenting at this time. But I can confirm that her son Michael, who is 19, died yesterday in Henderson, Nev."
Hunter Tylo has been a cast member of the soap on and off for 16 years.