The inquest into the death of Garda Tony Golden has heard that the fatal shot was into his back.
The inquest opened this morning in Dundalk, Co Louth.
Garda Golden was shot by Crevan Mackin at a house in the village of Omeath, on 11 October 2015.
Dr Michael Curtis, who performed the post-mortem examination, told the inquest hearing that Garda Golden had been shot five times - four times while facing the gunman - and the fatal shot was through the back.
He said this would have been "rapidly or instantaneously fatal."
Mackin also shot his partner Siobhan Philips, critically injuring her, before killing himself.
Evidence from Siobhan Philips, read out at the inquest of Garda Tony Golden, has heard how Crevan Macken subjected her to a periodic assault from 5pm until 7am, two nights before Craven Macken shot and killed Garda Tony Golden.
Ms Philips's evidence described how Craven Macken was quiet when she returned from work and was contacting another girl, who told him she would not talk to him anymore because he was a paedophile.
Craven Macken told Ms Philips this was all her family's fault.
Throughout the evening and night he punched her, cut her with a knife, kneed her in the ribs, and strangled her.
According to Ms Philips' evidence, the next morning, he told her to put on makeup and go to work.
The next day she contacted her father and stepmother, and attended the Garda station, where she was advised to seek medical attention.
The inquest also heard evidence from Sean Philips, the father of Ms Philips.
He told the coroner’s court that he was very "agitated" that a statement had not been taken.
He also described making contact with Garda Tony Golden the next day, and how Garda Golden took a statement and told her she should not be intimidated, while also suggesting going to the house with her to collect clothes.
Sean Philips said that he stayed in the car when Siobhan Philips and Garda Golden went into the house, and about one minute later he heard three bangs and then three more.
He told the court he would never have gone to the house if he knew Craven Macken had a gun.
"I never knew one thing about this guy having weapons...I now know Siobhan knew," he said.
"Macken was a monster and we want to know why he was out of jail," he added.
Sinead Hynes, a sister of Craven Macken, gave evidence to the court that he had been a difficult child and his behaviour was not normal.
She said his behaviour got worse as a teenager when he began breaking into houses.
He was later committed for a time, and his family moved to Australia without telling him.
She said he moved into Simon Community accommodation and that was when he fell in with republicans.
Craven Macken met Siobhan when she was 16 or 17 and she got pregnant about four months after.
She described how their relationship was fractious and that she knew that Craven Macken had been violent towards Siobhan and that she saw a bruise on her ankle that happened when she was injured with a firearm.
Craven Macken was out on bail at the time of the murder of Garda Tony Golden.
The inquest continues.