(CNN) -- The medical examiner has ruled that the death of Daniel Kerrigan, the father of skater Nancy Kerrigan, was a homicide, the Middlesex, Massachusetts, district attorney's office said Tuesday.

The Kerrigan family said in a statement that it was "extemely disappointed" in the medical examiner's "premature and inaccurate" ruling. The statement, issued by family attorney Tracy Miner, pointed out that Daniel Kerrigan suffered from a pre-existing heart condition.

Kerrigan's brother is behind bars, accused of assault and battery against 70-year old Daniel Kerrigan.

Daniel Kerrigan died last month after being taken by emergency personnel from his family home in Stoneham, Massachusetts, to a hospital. His son, Mark, has pleaded not guilty to charges stemming from an alleged assault.

Authorities have said in court that there was a violent argument and struggle between the father and his son, resulting in the elder Kerrigan falling or collapsing on the kitchen floor.

According to prosecutors, Mark Kerrigan admitted to authorities that he grabbed his father around the neck during an argument and the older man fell to the floor.

There was no immediate word on whether more serious charges would be filed against Mark Kerrigan in light of the medical examiner's ruling.

Prosecutors said police found Mark Kerrigan in the basement of the house, "clearly intoxicated" and "extremely combative" after the alleged attack. Police had to subdue him with pepper spray before forcibly removing him from the home.

Mark Kerrigan was unemployed, was recently released from a correctional facility and was living at home with his parents, his lawyer said at an earlier court hearing. He is taking medications and seeking psychological help for post-traumatic stress, apparently from his time in the Army.

Kerrigan is being held on $10,000 cash bail. His next court appearance is expected to be February 24.

Nancy Kerrigan first gained prominence by winning a bronze medal at the 1992 Winter Olympics in Albertville, France. In 1994 she earned an Olympic silver medal in Lillehammer, Norway. But she is perhaps best remembered for surviving an attack before the 1994 Winter Games by skating rival Tanya Harding's ex-husband and an accomplice.