Allowing John Carthy breach the inner perimeter around his home would not have been permitted in the United States, according to the FBI report on the Garda handling of the Abbeylara siege.
The five-page report criticises the Emergency Response Unit for letting Mr Carthy walk "undeterred" beyond the garden wall towards unarmed gardai at the outer perimeter and placing them in "serious danger". Mr Carthy was shot four times by gardai outside his home on April 20th.
"To allow Mr Carthy to cross the inner perimeter armed after he had repeatedly ignored warnings and had previously aimed and fired his shotgun at Garda officers was inconsistent with accepted law enforcement practices in the United States," it says.
It acknowledges that armed gardai at the scene "exercised restraint even though Mr Carthy repeatedly aimed and fired his weapon". They "appropriately used deadly force to protect themselves and others".
Five FBI agents, part of the force's Shooting Incident Review Team (SIRT), began their investigation on May 30th, and two members visited the scene of the shooting in Abbeylara, Co Longford.
The findings were forwarded to the Garda Commissioner, Mr Pat Byrne, on June 29th.
The agents examined statements of witnesses and gardai involved, video, photographs, pathology reports and incident sketches. The team did not interview the Carthy family, gardai at the scene or other witnesses.
The decision of the Assistant Commissioner, Mr Tony Hickey, to call in the ERU was described in the report as "appropriate" because of Mr Carthy's random firing and refusal to co-operate.
The Garda operational response plan for the siege was "tactically sound and well communicated", and the scene commander made clear the aim was containment and a negotiated peaceful resolution.
"Given his documented behaviour and refusal to co-operate with Garda instructions to surrender his weapon, Mr Carthy's escape would have constituted a threat to the public," the report adds.
However, the report is critical of two Garda detectives who drove to the house in an unmarked car to try to speak with Mr Carthy, and says the officers had placed themselves in unnecessary danger.