The victim has been identified as 49-year old Victor Lopez from Round Lake Beach, according to the Lake County Coroner's Office.
When first responders arrived, a friend was said to be performing CPR on him. The Marine Unite attempted to resuscitate the man until paramedics arrived.
He was transported to Advocate Condell Medical Center in Libertyville where he died.
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Lopez had been swimming in an area known as "The Sandbar" near north suburban Lake Villa when he went under on Friday, according to officials.
He was a Palatine police officer, according to a report from our news partners at the Daily Herald.
An autopsy determined he drowned.