The Hennepin County Medical Examiner says he died from complications of drowning.
A caregiver lost sight of the child, the sheriff's office said.
It happened at a rural home near the Iowa border in southeast Minnesota.
Jeylon Holloway was bringing his dog for a walk when he fell into the lake.
The lake is located within Bemidji's city limits.
Their child drowned while they were shopping for groceries.
The fire captain was kayaking when he leapt into action.
The 2-year-old died June 18.
The 40-hour search came to an end Monday morning.
The man fell from the boat around 3:20 p.m. Tuesday, according to the sheriff's office.
The 18-year-old's identity was released Tuesday afternoon.
The tragedy happened near the Clearwater Dam on Monday afternoon.
A witness saw the 24-year-old fall off the tube into the water.
The man drowned in Lake Victoria in late May.
The drowning happened at a public swimming area.
An online fundraiser aims to help cover funeral expenses for the family.
Deveric Stokes was just 29 years old.
The search was activated around 7:40 p.m. Tuesday.
The swimmer had jumped in the lake to help someone else who was struggling, but didn't get back on the boat.
There were also three water emergencies in St. Louis County.
He was confirmed dead at Regions Hospital.
A man was heard struggling in the pond two days earlier.