There was a huge outpouring of grief here last week as the murdered Irish police officer Garda Tony Golden was laid to rest. His funeral in the little seaside village of Blackrock, Co. Louth was attended by over 4,500 Gardaí – what one paper here called "a sea of blue" – as well as by all the leaders of the state from the president on down, and relatives and local people.

That is what happens here on the very rare occasions when one of our gardaí is killed. The country comes together to show support for our unarmed police force that holds a special place at the heart of the community here.

Despite being put in difficult and thankless situations sometimes recently, like having to protect water meter installers against violent radical protestors, the fact is that there is an extraordinary bond here between our police and our people. The recent closure of many small garda stations around the country has not helped, and there have been complaints about the failure to stop mobile gangs which target people in isolated rural areas. But even so, that remarkable bond is still very much intact.

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As one paper here put it last week, we are policed by consent, not by force. People here relate to gardaí almost as part of their extended families, something that is reinforced by the fact that so many of the young men and women in the force are from typical Irish families in rural areas. So when a garda is murdered as Tony Golden was ten days ago, the hurt and the sense of loss is deeply personal.

The circumstances of this killing two weekends ago were particularly tragic. As you may know from news coverage, Golden had accompanied a young woman, Siobhan Phillips, to her home in the village of Omeath to collect some of her belongings. She had been severely beaten in the previous days – and over a longer period – by her partner and the mother of her two young children, a 24-year old republican thug called Adrian Crevan Mackin, and she was in the process of leaving him. When she told him this he reacted by threatening to shoot members of her family.

She had told her relatives she was in fear of her life. With her father and other relatives she went to the small garda station in Omeath to register an official complaint against Mackin. Her statement was taken by Garda Golden, who then accompanied her back to her house to collect some things she needed for herself and the children.

When they entered the house they were confronted by Mackin, who shot and severely wounded Siobhan and shot and killed Tony Golden, before then shooting himself.

Given what was already known about Mackin, Garda Golden had been cautious in his approach, telling Siobhan's father to wait in the car while they went inside. But despite the young thug's reputation, such a ferocious reaction by him to the situation was completely unexpected.

What ensued was carnage as Mackin blasted away at his partner and the unarmed Golden and then committed suicide. As this is written, Siobhan Phillips is still in critical condition after being shot in the head and may never fully recover. It's tragic, as we have said.

But there is a wider context here. What happened is also indicative of an ongoing problem we have with criminality in the border area associated with the remnants of Republican activity.

Omeath is just a few miles from the border with Northern Ireland, and it's no accident that that is where Mackin, originally from the North, had chosen to live. The so-called border corridor on both sides has been an area of ongoing criminal activity associated with Republicans of various brands ever since the IRA ended its war in 1994.

Adrian Crevan Mackin was a disturbed young man, with a head full of notions influenced by this ongoing Republican activity, even though he was just three years old when the IRA finished what it called "the war." It is one of the worrying aspects of our recent history that the criminal aftermath and thuggery left behind in the wake of the IRA campaign frequently involves young men like Mackin who were not even born when the conflict in the North was at its height.

At the time of the shooting, Mackin was out on bail on a charge of IRA membership and was signing on at Dundalk garda station three times a week. He was well-known to both the gardaí and the Police Service of Northern Ireland (PSNI) for his involvement with a faction of the Real IRA, and he was hanging around with the heavies in various paramilitary gangs on both sides of the border.

Here he was charged with membership of an unlawful organization at the Special Criminal Court in January this year and was out on bail pending trial. In the North he had been given a suspended sentence after he was found guilty of having a handgun in Newry two years ago.

He had also been given a suspended sentence in the North in 2012 for possession of images of extreme pornography, including bestiality. He also had a history of beating up his partner when they lived in the North, and at one point he had threatened to kill two social workers in the North who were investigating him for domestic abuse.

As well as being clearly disturbed, he had a fascination for and a skill with guns. He had been buying deactivated handguns on line from the U.S. and then separately ordering replacement parts and restoring the guns before passing them on to Republican criminal gangs. The weapon he used to kill his partner and Garda Golden was a Glock handgun which may have been restored to working use in this way.

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All told, Mackin was a sad case and a dangerous fantasist. It appears that he was so unstable that even the Republican heavies he was trying to hang out with didn't trust him and kept him on the fringes.

The worrying aspect of this is that there are a good many young men like Mackin in the border area who are infected by the lawless culture that pervades there. It is this milieu along the corridor from the Bandit Country of South Armagh in the North to Dundalk in the south, the last big town on this side before you cross the Border, that allows them to maintain a beyond-the-law lifestyle. They are attracted by the status it gives them and by the easy pickings. They hope to ingratiate themselves with the main Republican godfathers of crime in the area and one day become one of the big guys themselves.

All this is a direct result of the criminality that has been carried on in the area by many of the former IRA gunmen and the various dissidents and breakaway groups ever since the ceasefire over twenty years ago. What used to be fundraising for the cause deteriorated over time into ordinary criminality.

These days there are major fuel smuggling, diesel washing and cigarette smuggling operations being carried out by these mobs, mainly on the northern side of the border but with connections and facilitators on this side. In addition to this there are ongoing protection rackets and other "security" related operations that extract cash from legitimate businesses and criminals like drug dealers. All told, it has been estimated that such operations produce tens of millions in funds each year for the gangs involved.

Clashes with the PSNI and Gardaí are rare, although it is only two years since another Garda, Adrian Donohoe, was shot dead in a cash raid on a credit union in the same North Louth area, an operation carried out by a Republican criminal gang. No one has been brought to justice for this killing, which shows the level of control in maintaining silence still exerted by the Republican gang structures.

One of the most worrying aspects of all of this is that the governments on both sides of the border have been involved in an unspoken trade-off. In return for the ending of the bombings and shootings that were part of the IRA campaign, the two governments have been less forceful than they might have been in ending the ongoing criminality and lawlessness in areas along the border corridor.

It's not a question of turning a blind eye. It's more a matter of priorities and resources.

South Armagh may no longer be a no-go area for the PSNI, but that does not mean they want to go there that often or get involved too deeply in ways that might be very dangerous. And it's a similar story on our side of the border, where the money that flows from smuggling and other Republican criminal activity corrupts some people and makes them two-faced in their attitude to the gardaí and law and order.

In response to this latest killing, there are to be a few dozen extra gardaí assigned to stations in border towns and villages, to restore the numbers of gardaí that were lost during the recent cutbacks. It's a start, but there is a very long way to go before this part of Ireland can finally be rid of the corrupt legacy left by the Republican war along the border corridor.