In his first public comments about a letter sent to his office from someone who may have tried to torch his Michigan vacation house, Mayor Richard Daley described the correspondence as "personal" and "very, very vicious."

He said he is concerned about his family's safety but is not worried about returning to his lakefront cottage in Grand Beach, Mich.

"You wonder how people can get so—hatred, hatred, and that's what it is," Daley said Saturday at a news briefing. "You worry about your family. I love public life. I love being mayor, and these things are difficult to deal with."

On April 24, an arson fire swept within a few car lengths of the Daley family's cottage, then surged through dry dune grass toward the properties of two neighbors, gutting one home and destroying the garage of another.

Daley's house was not damaged, and there were no injuries. No suspects are in custody.

Investigators, including the FBI, are looking into whether there is a connection between the fire and letters threatening Daley, possibly because Chicago police shot a cougar on the North Side on April 14.

"These letters appear to be written by the same group or individual and threaten physical harm to specific individuals and entities in connection to the recent shooting of a wild cougar in Chicago last month," the FBI said Friday in a statement.

The mayor's office received a threatening letter before the fire, which prompted an investigation, officials said. State officials ruled the fire an arson Tuesday.

In late April, a letter was sent to Audubon Elementary School, a block from where the cougar was shot in Roscoe Village. The writer made angry references to the cougar shooting and the families of Daley and Police Supt. Jody Weis. The letter also contained anti-Semitic references.

Police said they shot the animal after it lunged at an officer.

In response to the shooting, Daley said: "Now I just want to tell you if the cougar attacked a child, they'd sue the city because the police officer didn't do their job. I didn't see a neighbor run out and grab it and say, 'Oh, I love you,' and bring it in the house."

Daley has a security detail while he is home in Chicago. His office declined to comment Saturday about possible changes to his security detail.

Staff reporter Dan Mihalopoulos contributed to this report.