Two Iowa men authorities say threatened gun violence at the Pokemon World Championships in Boston have been arrested.

Eighteen-year-old Kevin Norton, of Ames, and 27-year-old James Stumbo, of Boone, were held without bail on gun charges pending a September 1 hearing to determine whether they are a danger to society.

Authorities say the suspects referenced Columbine and the Boston Marathon bombing on social media. They were stopped on Thursday as they were about to register for the event.

They were released, but their car was seized after authorities learned they might have guns.

Officers executing a search warrant found a 12-gauge shotgun, an AR-15 rifle, several hundred rounds of ammunition, and a hunting knife in the car. Norton and Stumbo were arrested at their hotel.

The Pokemon cartoon franchise includes card trading and video games.

PA Media