Boston police have arrested two men heading to the Pokémon world championships after firearms and several hundred rounds of ammunition were allegedly found in their car.

The men were originally suspected of making violent social media threats to people attending the gaming event in Boston. Security at the convention reported the threats on Thursday and the suspects were stopped as they were about to enter the gaming event hours later, Boston police said.

Police said they released the men, who were from Iowa, but seized their car after learning they might have guns inside.

Police said a warranted search of the car on Friday found a 12-gauge shotgun, an AR-15 rifle, several hundred rounds of ammunition, and a hunting knife. Police said 18-year-old Kevin Norton, of Ames, and 27-year-old James Stumbo, of Boone, were arrested at their hotel in Saugus, north of Boston.

They are being arraigned on firearms charges on Monday. It is not immediately known if they have attorneys.

Associated Press contributed to this report