Authorities on Thursday said they were working to confirm if a man who claimed to have slain a federal judge's husband and mother before killing himself was telling the truth.

"We are attempting to learn as much as we can about Bart Ross's (search) history: who he was, who he was associated with, and what he was doing in the days leading up to these murders," Chicago Police Chief Phil Cline said in an afternoon press conference.

Ross, who was apparently angry at Judge Joan Humphrey Lefkow (search) for dismissing a lawsuit he'd filed, shot and killed himself Wednesday night during a traffic stop in West Allis, Wis. A suicide note in which he confessed to killing Lefkow's husband and mother was found in his vehicle.

And on Thursday, a local TV station announced that they had received a handwritten letter signed by Ross outlining the murders. FBI and local crime labs were trying to confirm if Ross was indeed the author, Cline said.

Cline declined to call Ross a suspect, saying it was premature to do so. Because Lefkow had presided over a case involving him, authorities had already intended to question him, Cline said.

Police and FBI agents were hoping for a match as they analyzed evidence in Ross's vehicle and home as well as Lefkow's home.

"We're satisfied that there's information in the letter that would point us to Ross being in Lefkow's house," Cline said.

But, he said, "we still have many facts to gather."

Ross, a 57-year-old electrician, had sued a hospital over cancer treatments he received more than a decade ago that left him disfigured. He had already lost one lawsuit, and last year Lefkow dismissed another on a technicality.

"Since Feb. 16, 2005, I lived in my car moving around, and when I got numb enough to care about nothing, I finally did it on Feb. 28, 2005," the letter sent to WMAQ read.

Lefkow's husband, Michael Lefkow, 64, and her mother, Donna Humphrey, 89, were found dead on Feb. 28.

"Judge Lefkow was No. 1 to kill because she finished me off and deprived me to live my life through outrageous abuse of judicial power and decicration [sic] of the judicial office. Judge Lefkow, to her neighbors, is a church going 'angel'. To me, Judge Lefkow is a Nazi-style criminal and terrorist," the letter read.

The author also wrote that the judge was his intended target, and seemed remorseful her husband and mother were killed instead.

"I regret killing husband [sic] and mother of Judge Lefkow as much as I regret that I have to die for the simple reason that they personally did to me no wrong," the letter said.

The author wrote that he had broken into Lefkow's home and intended to wait for her, but was discovered by her husband, Michael Lefkow (search). After shooting him, the author says he was also forced to shoot the judge's elderly mother, who was the only other person in the house.

Lefkow and her four daughters have been under police protection since the killings.

Confessions of a Killer?

Details in the letter and in the suicide note found in Ross's vehicle seemed to match.

The suicide note was not released and included unreported details about the murders. The note said the legal judgment had cost Ross "his house, his job and family," the Chicago Tribune quoted a source as saying.

The author of the letter sent to WMAQ implied he planned to kill himself, and said he had lost his home and was living in his car.

The letter also said he used a ".22 with a noise reducer relatively quiet and effective," to kill Lefkow's husband and mother.

Shells of the same caliber were found in Ross's van, the Tribune reported. The casings found in Lefkow's home were also .22-caliber.

The author of the letter said that he intended to kill more people, including a doctor and another judge, but eventually decided against it. A list of people Ross thought had mistreated him was found in his vehicle. The list included the names of judges.

Cline refused to characterize the paper as a "hit list," but said authorities were trying to contact every person on the list.

A typewritten letter describing Ross's court battle was also sent with the handwritten note. Ross had filed a lawsuit against the University of Illinois over cancer treatment in the early 1990s, the newspaper said. Lefkow rejected it on a technicality in 2004.

"When you read this I should be dead, so I am writing in past tense. I was on my way to Justice. For over 12 1/2 years I was violated the way Nazis and terrorist violated peoples [sic] rights and I was deprived 'to live' my life," the letter began.

West Allis Police Chief Dean Puschnig told reporters in Wisconsin on Thursday that Ross's vehicle, which had Illinois plates, was stopped because its taillights were out.

"While approaching the driver, a single gun shot was fired from inside the vehicle," Puschnig said. "The bullet exited the vehicle very close to where the officer was standing."

Puschnig said that when other police arrived on the scene, material was found inside the van "that led us to believe that this man could be involved or have some information relevant to the Lefkow investigation."

Chicago police cordoned off the street outside Ross's last known address Thursday morning, a two-story home across from a high school on a tree-lined street on the city's North Side. Investigators were combing the home for DNA and fingerprint evidence and questioning neighbors.

James Finch, head of the Milwaukee FBI office, said federal agents there would not scale back their investigation because "we have not definitively tied this individual to the Lefkow murders."

"Until such time as we determine whether this individual is the sole perpetrator, we have to continue our investigation," Finch said.

Last week, police released sketches of two "persons of interest" in the case. Ross did not seem to match either of their descriptions.

Jailed white supremacist Matthew Hale (search), convicted of soliciting an FBI informant to kill the judge, had been an early focus of the investigation. He denied playing any role in the deaths.

An attorney for Hale said Wednesday that Hale's mother asked him late last year to relay a coded message from Hale to one of his supporters. Lawyer Glenn Greenwald said he declined to deliver the message.

Hale is set to be sentenced next month.

A Man Obsessed

Ross had emigrated from Poland in 1982 as Bartlomiej Ciszewski, changed his name and became a U.S. citizen in 1988, according to the U.S. Citizenship and Immigration Service.

But when Lefkow came home from work on Feb. 28 and found the bullet-riddled bodies of her husband and mother in her basement, all eyes were on Hale

Hale was known to have plotted to kill the judge before. And for that reason, the white supremacist said, "Only an idiot would think I would do this."

Ross's suicide seem to be the first big break in the case.

Last September, Lefkow dismissed a civil rights lawsuit in which Ross claimed doctors at the University of Illinois-Chicago Hospital had disfigured him, damaged his mouth and caused him to lose his teeth when they treated him for cancer from 1992 to 1995. A federal appeals court affirmed Lefkow's decision Jan. 21.

Among other claims, Ross alleged doctors committed a "terrorist act" against him by giving him radiation treatment without his consent. He represented himself in the lawsuit.

Defendants in the lawsuit included the federal government, the State of Illinois, five doctors and four attorneys who had taken part in an earlier Ross lawsuit that was dismissed by another judge.

Ross blamed the justice system for his problems and demanded Congress impeach four judges for failing to reform the justice system and denying his petition to move his case to a higher court. He compared the radiation therapy and surgery he received to experiments performed by Nazi doctors and said the United States inflicted on him "Nazi style and magnitude additional catastrophic injuries and damages."

Ross also complained about the legal system in letters to President Bush, U.S. Sen. Richard Durbin, D-Ill., former U.S. Sen. Peter Fitzgerald, R-Ill., and U.S. Rep. Luis Gutierrez, D-Ill.

"As his legal remedies were becoming fewer, as he had less success, he became more angry, more agitated," said Chicago lawyer Thomas Browne, who represented an attorney Ross was suing.

Court records show Ross was also being evicted from his home and had a court date Thursday.

Jinky Jackson, 34, who lives one house down from Ross, said Ross was wearing a neck brace as of a month ago. She said she would say hello to Ross when she saw him but he would not reply.

"He doesn't mingle with other neighbors," Jackson said. "He'd come home late and stay inside."

FOX News' Jane Roh and The Associated Press contributed to this report.