An Ohio man who was an ardent participant in the live-action role playing game Dagorhir built a pipe bomb and delivered it to his ex-girlfriend’s boyfriend in Maryland, where it exploded and seriously wounded the victim, NBC News reports.

Clayton Alexander McCoy, a 30-year-old resident of Chesterland, Ohio was arrested and charged Thursday with transporting an explosive device with intent to injure and using a destructive device in a violent crime, according to a federal criminal complaint outlining the October 30th attack.

McCoy’s ex-girlfriend “has known McCoy for approximately seven years, since McCoy became a member of the Dagorhir community,” according to Dawn Machon, a special agent with the Bureau of Alcohol, Tobacco, Firearms and Explosives.

Dagorhir is a live action role playing game in which participants dress in Medieval attire and engage in full-contact battles using foam weapons such as swords, flails, spears, bows & arrows, javelins and axes.

Jim DeWees, the sheriff of Carroll County, Maryland where the bomb went off, likened Dagorhir to Civil War re-enactments.  Law enforcement was able to track McCoy through his cell phone, putting him in the area when the package was delivered.

According to NBC News, McCoy was convicted in 2013 of sharing child pornography online with an undercover investigator, according to federal authorities and Geauga County, Ohio, prosecutors.  He was sentenced to four years in prison and forced to register on the state’s sex offender registry.