Ciaran Maxwell, 31, is a Northern Irish Catholic who stockpiled and made handguns, anti-personnel mines, pipe bombs and chemicals to make explosives, all while serving in the British military.
Authorities believe Maxwell is the first active soldier to be arrested on terrorism charges, though they say there’s no evidence to suggest he was trying to infiltrate the military.
Militants carrying out attacks in Ireland used Maxwell’s devices, according to Assistant Chief Constable Stephen Martin from the Police Service of Northern Ireland (PSNI).
Martin said, "There is a strong likelihood that items associated with Maxwell have made their way into the hands of violent dissident republican groups in Northern Ireland and four of these items have been used, three in the last year … Not all of those devices detonated. Some did."
Some dissident Irish nationalist groups continue to function and sometimes still carry out shootings and bombings, despite the general end of three decades of violent conflict between Republican Catholics and pro-British Protestants with the 1998 Good Friday accord, a political agreement that addressed deep issues between Northern Ireland, the Republic of Ireland and the United Kingdom.
In February, Maxwell admitted to making preparations for terrorist acts, possessing bank cards and IDs he’d stolen from his fellow marines, possessing articles that would allow him to commit fraud and possessing marijuana with intent to supply.
When Maxwell was 16, he suffered a violent attack in his hometown of Larne, north of Belfast, at the hands of pro-British Loyalists, but it isn’t clear whether this was a factor in his behavior.
His guilty plea will earn him a 30 percent reduction on his 18-year sentence, according to authorities.
Martin said, "I think it would be wrong for us to speculate about a motivation," Reuters reported.
First joining the Royal Marines in 2010, Maxwell eventually found himself in the 40 Commando unit based in southwest England. Evidence suggests he had already began researching how to make explosives by 2011.
He managed to fly under the radar until a civilian discovered two blue barrels containing bomb-making materials north of Larne in Carnfunnock country park.
Three more barrels were discovered by another civilian two months later in a woodland area west of Larne, with DNA evidence connecting Maxwell to the materials leading to his arrest at Norton Manor army camp in August.
Nineteen other stashes were found during the course of a search near his home near Exminster.
Police found two explosively formed projectiles (EFP) designed to take out armored vehicles, 14 pipe bombs, two homemade anti-personnel mines, two handguns and other materials.
Martin told reporters, "You only gather an array of materials like this for one use … That’s to cause harm, destruction and potentially death."
Despite the expansive horde of weapons, authorities say as of now it appears Maxwell acted alone.