Anthony Hensley, 37, kayaked out to the middle a pond, never to return alive. After being attacked by a vicious swan, Hensley rolled his kayak into the water, where he drowned on Sunday.

Cook County sheriff's investigators believe Hensley approached the swan or its nesting areas. The bird may have felt threatened as he kayaked near the Bay Colony condominiums in Des Plaines, Ill. Witnesses said that the swan continued to go after Hensley after he tried to make it to the shore and leave the animal alone, reported the Sun Times.

On Monday, details were not available about the swan that attacked Hensley. Swans can grow to be quite large, standing about 4 feet tall, weighing 30 pounds with a wing span up to 8 feet wide, reported the L.A. Times.

Hensley's family was reportedly grief-stricken as they struggled to make sense of the tragedy. They were unable to understand how he could not fend off the bird.

Maybe he didn't want to hurt the animal, Hensley's father-in-law, George Koutsogiannis, told the Sun-Times. Maybe he didn't fight back enough when the swan attacked him.

While swans are often seen as peaceful and serene birds, they are territorial. They can become aggressive, if they believe they or their young are threatened, reported the L.A. Times.

As the swan attacked Hensley, he rolled into the pond. Frank Bilecki of the Cook County Sheriff's Department said Hensley struggled to stay above the water, reported ABC News.

Witnesses reportedly saw Hensley resurface a few times and called police. However, by the time emergency workers arrived at the scene, they found him submerged. He was not wearing a life vest.

An autopsy revealed that he died from drowning.

Hensley works for a company that uses dogs and swans to keep geese away from properties in the area. He had rowed into the lake to check on the swans when one attacked.

A memorial fund was established in the wake of Hensley's death; he was married with two children. Donations can be made to Amy Hensley, c/o Steuerle Funeral Home, 350 S. Ardmore Ave. Villa Park, Ill. 60181.