ISLAND LAKE, Ill. (CBS) – Police have decided not to seek criminal charges in the case of a 2-year-old boy who drowned Sunday night in a lake behind his far northwest suburban home.

Detectives are calling his death a “tragic accident.”

Mason Mack, of the 200 block of Fairfield Drive in Island Lake, was pronounced dead at 3:25 a.m. Sunday at Advocate Lutheran General Children’s Hospital in Park Ridge, the Cook County Medical Examiner’s office said.

Island Park police and the Lake County Major Crimes Task Force investigated and announced Tuesday they are not seeking criminal charges in connection with Mason’s death, the release said. Counselors were also made available to officers following the “tragic incident.”

At 10:49 p.m. Sunday, the child’s father Scott A. Mack called 911, telling police his son was missing and wearing only a diaper, a release from Island Lake police said.

The boy’s father — holding his son in his arms — flagged down police when they responded to the family home, and officers performed CPR on the boy, the release said.

Paramedics also responded to the home and initially took the boy to Advocate Good Shepherd Hospital in Barrington but he was soon transferred to Lutheran General, Wauconda Fire Protection District Batallion Chief Kevin Pyne said.

Pyne said the boy was unresponsive, but had a pulse, when he was taken from his home.

His father told police that he had fallen asleep in the living room for about 20 minutes while his son was still awake, and began searching the house when he woke up and realized the front door was no longer locked, the release said. He found the boy in a lake in the home’s back yard.

A Monday autopsy confirmed the boy drowned, but did not rule on the manner of his death, the medical examiner’s office said.

Despite the decision not to seek charges, Illinois Department of Children and Family Services spokesman Jimmie Whitelow said the agency’s allegation of neglect against Mason’s father is still ongoing Tuesday per department policy. DCFS had no prior contact with the family prior to the incident.

The Sun-Times Media Wire contributed to this report.