"Demi is shocked and upset by the news. She's really sad about it," a source close to Moore tells PEOPLE.
The actress, 52, was in Paris at the time of the incident, and her daughters with Bruce Willis – Rumer, Scout and Tallulah Willis – were in New York City, the source says.
According to the Los Angeles County Coroner's office, a caretaker of Moore's property invited the man who drowned, Edenilson Steven Valle, to the house for a small party.
"They were sitting by the pool and the party stopped around 2:30 a.m. and at 5 o'clock one of the people at the house found him at the bottom of the pool," L.A. County Assistant Chief Coroner Ed Winter tells PEOPLE. "The caretaker and her boyfriend were there and they invited some people over. According to the witnesses, he had a couple of beers. He was not a big drinker and he said he didn't know how to swim very well."
“He always seemed very happy," high school friend Danny Ramirez tells PEOPLE. "He always had a smile on his face."
Friends have posted remembrances of Valle on social media.
Rest in peace Edenilson pic.twitter.com/w0tAYxrnJn— zari (@zarigensmom) July 20, 2015
I'm in shock right now. You were such a chill and nice person. RIP Edenilson— Crisssy (@crystallyvette_) July 20, 2015
such heartbreaking news Rest in peace Edenilson.— m (@mmmmfranco) July 20, 2015
"I am in absolute shock," Moore said in a statement shortly after the news broke. "I was out of the country traveling to meet my daughters for a birthday celebration when I got this devastating news.
"The loss of a child is an unthinkable tragedy and my heart goes out to this young man's family and friends," she continued. "I ask that you please respect the privacy of all concerned during this sensitive time."
Reporting by AILI NAHAS and CHRISTINE PELISEK