Boston police arrested two men they say drove from Iowa to the city to carry out threats of violence on the Pokémon World Championships being held there this weekend. Firearms and ammunition were found in their possession.

Boston police said the two suspects — Kevin Norton, 18 and James Stumbo, 27, both of Iowa — had made threats against the Pokémon World Championships over social media. They were stopped at the Hynes Convention Center attempting to enter the event, they said.

The specific nature of their threats was not immediately clear. Police said private security officials became aware of them through social media and notified authorities on Thursday.

On Friday, the two men were stopped attempting to enter the event. They could not produce any license to carry the firearms that were said to be in their vehicle, and police released them pending a search warrant.

On Friday, cops executed that warrant and from the vehicle recovered a semiautomatic AR-15 assault rifle, commonly referred to as the civilian equivalent of the U.S. military's M16, and a 12-gauge Remington shotgun (pictured above). A hunting knife and "several hundred rounds of ammunition" also were found in the vehicle.

Police later arrested the two men at a hotel in Saugus, Mass. They have been charged with unlawful possession of a firearm, unlawful possession of ammunition, and "other firearm related charges," Boston police said. They will be arraigned later in municipal court.

"This incident is a good example of private security reaching out to their local Boston police district and relaying information to detectives and BRIC analysts in order to identify the very real threat," Paul Fitzgerald, the superintendent of the Boston Police Department's Bureau of Intelligence and Analysis, said in a statement. "The BPD detectives and collaborating agencies did a great job in the stop and prevention of a potential tragedy."