The 39-year-old died in hospital on Sunday, six days after the alleged assault. The incident is reported to have taken place at a location in Newtownards, Co Down.
The flat jockey was based in the UK for a decade between 2005 and 2014, and had more than 60 winners throughout his career.
His last ride was at Wolverhampton in October 2014. His final victory came the previous June on a horse named Hamble.
A statement from the Police Service of Northern Ireland (PSNI) confirmed that detectives were investigating all the circumstances surrounding the death of a man in his 30s.
They said: "The man died in hospital on Sunday, following an incident at a house in Stratheden Heights, Newtownards, on September 7. There are no further details at this time."
Joseph Donaghy, the brother of the late jockey, 46, appeared at Newtownards Magistrates Court last week charged with causing grievous bodily harm in relation to the incident.
Mr Donaghy is survived by his parents, John and Sarah, and siblings Joseph, Brona and Sarah, and Brona’s husband Simon.
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Tributes poured in on social media for the late jockey. His cousin Gerard said "My heart aches in a way that I can’t really put into words."
"There is some comfort in knowing there was no pain, Paddy — nothing but love, with your family surrounding you right until the end," Gerard wrote.
"Since you were wee, you were full of imagination. Playing jockeys, farms, dress up. And you never lost that playful spirit. You always found a way to make people laugh, create a bit of craic and turn an ordinary moment into a memory."
His death notice read: "A loving and devoted father of Lennon, a dear uncle to his many nieces and nephew. RIP."
Mr Donaghy’s funeral service will take place in St Patrick’s Parish Church, North Street, Newtownards on Friday, September 18, at 11am, followed by committal in Movilla Cemetery.
* This article was originally published on Extra.ie.