Mark Kerrigan, a 45-year-old unemployed plumber, allegedly used his bare hands to throttle their dad Daniel, 70, because he would not let his son make a phone call.
Mark was so drunk and unruly when police arrived about 1.30am on Sunday that police said they had to subdue him with pepper spray.
The details are spelled out in police documents lodged in a Boston court yesterday.
Mark Kerrigan was charged with assault and battery with a dangerous weapon on an elderly person and causing serious bodily injury. He was not charged with murder.
Kerrigan, who wept during the brief hearing, pleaded not guilty and remains in jail on $10,000 bail.
The Kerrigans' mother Brenda claimed her husband had died of a heart attack.
"This is a very difficult time for me," she said. "My God. He had a heart attack."
The coroner is still investigating the cause of death.
Tragedy is nothing new for the Kerrigans. Nancy, a two-time Olympic medallist for the US, is famous for a dramatic attempt to shatter her kneecaps before Olympic trials in 1994.
The ex-husband of her rival Tonya Harding hired a hitman to beat Kerrigan's knees with a baton before the event, provoking her cry of "Why me? Why, why, why?"'
Described by his attorney as an army veteran with post-traumatic stress disorder, Mark Kerrigan has a long history of petty crime.
He has been living at his parents' home since he was released from jail in 2007the Woburn District Court heard.
He spent four months in jail after a domestic assault in 2005 and has at least four drink-driving convictions.
Mark's parents tried to sue him in 2008, claiming he owed them $110,000, and for caring for his dogs. The case was dismissed.
A funeral mass for Daniel Kerrigan will be held Friday.
