He was arrested for allegedly overstaying on a travel visa and a date for his immigration hearing has not yet been set.
The suspect was arrested as part of US President Donald Trump's high profile crackdown on illegal immigration.
According to reports, two other men linked to the murder are living in Boston while the fourth splits his time between Newry and Dundalk.
It is believed that a former associate of the man, who is now living in Ireland, has been assisting gardai with their inquiries. A number of people who would have previously not spoken up about the murder are now cooperating with the investigation.
An Irish man arrested in NY is reportedly a person of interest in the murder investigation of Garda Adrian Donohoe.
Gardaí will also seek to question him in connection with the murder of Detective Garda Adrian Donohoe who was shot dead while on a cash escort at the Lordship Credit Union in Co Louth on 25 January 2013.
Significant information in relation to the Donohoe investigation has been obtained in recent months. The gang of five involved in the attack escaped the scene with just €4,000.
"An Garda Síochána is committed to ensuring Adrian's killers are brought to justice", Commissioner O'Sullivan said. However, in recent days there has been attempts to bring the suspected triggerman back to Ireland.
Chief Supt Sean Ward, of Dundalk garda station, said that An Garda Síochána was working with police forces in the U.S. and United Kingdom as part of the murder investigation.
He is now in custody "pending removal from the United States".