The Garda Special Branch are believed to have searched Adrian Crevan Mackin's home in Omeath after receiving a tip off from US authorities
The callous killer of a police officer in Ireland was involved in supplying reactivated handguns to terrorists and criminal gangs.
Adrian Crevan Mackin murdered dad-of-three Tony Golden and left the mother of his children fighting for her life in hospital before shooting himself in Omeath in Louth on Sunday evening.
His evil past included attempted murder and jail for possessing sick animal porn pictures, reports the Irish Mirror.
The 24-year-old had been ordering weapons online to receive by post from the US.
Mackin was also buying handgun parts online to reactivate the replicas as weapons, the Irish Independent reports.
The Garda Special Branch are believed to have searched his home in Omeath after receiving a tip off from US authorities in January.
Two of the re-purposed guns and items used for bomb-making were discovered, the publication reports.
Mackin was well-known to officers on both sides of the border and had been charged with membership of the IRA earlier this year and was on bail when the horrific murder took place.
He moved to Omeath in North Louth with Siobhan, 21, and their two children who are both under four, but their relationship has been described as volatile.
A pal revealed: "They were always breaking up, rowing and fighting.
"He was violent and in the end poor Siobhan was terrified, she just wanted away from him."
Thousands are expected to pay their respects to hero garda Tony Golden as he is laid to rest.
But the parents of Adrian Crevan Mackin who moved to Australia while he was in his teens are not expected to return home for his funeral.
And several funeral directors in his hometown of Newry have refused to take his body.
An uncle of Mackin told the Irish Daily Mail that his mother's side are "completely estranged from him".
He said: "His own mother and father are on the other side of the world.
"They aren't even coming home to bury him. He is not part of this family."