BOSTON — Olympic skater Nancy Kerrigan said Thursday that she and her family plan to help her brother fight a state medical examiner's finding that her father's death last month was a homicide after a fight.

Daniel Kerrigan, 70, died Jan. 24 after what authorities said was a struggle with his son, Mark, 45, who was charged with assault.

In a letter released Thursday, Nancy Kerrigan thanked friends and fans for their support and says the weeks since her father's death have been "a sad moment for us all."

"And it isn't over yet, particularly with the ruling this week about the cause of my dad's death; a ruling, by the way, which we think was unjustified and which we plan to help my brother fight," Kerrigan wrote in the letter.

Kerrigan released the letter the day before she is scheduled to begin work as a commentator on the Winter Olympics for "Entertainment Tonight" and "The Insider," as she did during the 2006 games.

Middlesex District Attorney Gerry Leone said Tuesday that an autopsy determined the cause of death for Kerrigan's father was "cardiac dysrhythmia" — a loss or interruption of a normal heartbeat that can lead to cardiac arrest — after a physical altercation with neck compression that damaged Kerrigan's windpipe. The findings also noted that the elder Kerrigan had high blood pressure and clogged heart arteries.

Kerrigan's family immediately issued a statement disputing the findings. They said Daniel Kerrigan had a pre-existing heart condition.

Leone said that as a result of the medical examiner's findings, the investigation is continuing into Daniel Kerrigan's death and "whether any charges in connection with his death are appropriate."

Mark Kerrigan has pleaded not guilty to a charge of assault and battery on an elderly person and is undergoing a psychiatric evaluation.

An attorney who represented Mark Kerrigan at his arraignment said he was an Army veteran who had served overseas, was on medication for post-traumatic stress syndrome and was seeing a psychiatrist.

Police said Mark Kerrigan told them he had an argument with his father over use of the phone.

"He said he struggled with his father and put his hands around his father's neck and his father fell to the floor," they said in a police report.

Mark Kerrigan has a lengthy criminal record, with convictions dating to 1991, including drunken driving, assault and battery, domestic assaults, resisting arrest and violation of a restraining order.

In the letter released Thursday, Kerrigan said her father was her "safety net," a doting grandfather and "the ultimate role model" for her two brothers — "the guy they continue to try to emulate."