ABC News' Ben Waldron and Colleen Curry report:
An angry swan is being blamed for knocking a man out of his kayak in a Chicago pond and then continuing to attack until the man drowned.
Anthony Hensley, 37, of Villa Park, Ill., worked for a company called Knox Swan & Dog which used swans and dogs to keep geese off the condominum's properties.
Hensley was in a kayak on the condo's retention pond checking on the animals Saturday morning when one of the swans swam at him, causing him to fall out of his kayak into the water.
Frank Bilecki of the Cook County Sheriff's Department, told ABCNews.com that Hensley struggled to stay above water. Two witnesses saw Hensley resurface a few times in the pond and called police, but by the time crews arrived he had been fully submerged. He was not wearing a life vest, Bilecki said.
The Chicago Sun Times reported that while Hensley struggled in the water, the swan continued to harass Hensley.
Dive teams pulled Hensley, a husband and father of two, from the water, but he was pronounced dead at a hospital shortly after.
Investigators believe Hensley had traveled too close to the swan or swan's nesting area, prompting the attack. Family and friends are puzzled.
"Maybe he didn't fight back enough when the swan attacked him," said father-in-law George Koutsogiannis. "Maybe he didn't want to hurt the animal. I can't understand how this was possible."
A memorial fund has been established in Hensley's name, who was a married father of two. Donations can be sent to Amy Hensley, c/o Steuerle Funeral Home, 350 S. Ardmore Ave. Villa Park, IL 60181.