(COEUR D'ALENE, Idaho) -- Police in a small Idaho city arrested 31 people allegedly affiliated with a white nationalist group near a Pride parade, authorities announced on Saturday.
People associated with the group "Patriot Front" allegedly had shields, shin guards and other riot gear with them, including at least one smoke grenade, Coeur d'Alene, Idaho, Police Chief Lee White said. They were charged with conspiracy to commit a riot.
The individuals were arrested after a citizen called police to alert them that at least 20 men were seen getting out of a U-Haul van wearing masks and carrying shields, White said.
Among those arrested was the founder of Patriot Front, Thomas Rousseau. Suspects are from Alabama, Arkansas, Colorado, Idaho, Illinois, Michigan, Oregon, South Dakota, Texas, Utah, Washington and Wyoming, according to information provided to the jail.
"It is clear to us based on the gear that the individuals had with them, the stuff they had in the possession and in the U-Haul with them along with paperwork that was seized from them, that they came to riot downtown," Chief White told reporters on Saturday.
The group, according to organizations tracking hate groups, has white nationalist ideologies that was founded shortly after the "Unite the Right" rally in Charlottesville, Virginia.
Javed Ali, the former senior counterterrorism director at the National Security Council told ABC News that members of the group "have been linked to various extremist causes and incidents over the past few years, and the recent arrests demonstrate the broad diversity in their geographic locations and individual backgrounds"
The Chief said the steps officers took prevented a riot.
"So preventing a riot by arresting and 31 people with a misdemeanor, I will gladly do that every day of the week," he said.
Paperwork, the Chief said "appeared to be very similar to an operations plan that a police or military group would put together for a day's for an event," was also found on the persons arrested, but did not elaborate any further on what it said.
Individuals who were arrested came from at least 11 states and as far away as Virginia, according to police.
The arrests come as the Department of Homeland Security warned last week the summer could be a "dynamic" threat landscape, and extremists could target public gatherings, faith-based institutions, schools, racial and religious minorities, government facilities and personnel, U.S. critical infrastructure, the media and perceived ideological opponents.
"In the coming months, we expect the threat environment to become more dynamic as several high-profile events could be exploited to justify acts of violence against a range of possible targets," the National Terrorism Advisory System Bulletin issued by DHS last week said. "Threat actors have recently mobilized to violence due to factors such as personal grievances, reactions to current events, and adherence to violent extremist ideologies, including racially or ethnically motivated or anti-government/anti-authority violent extremism."
John Cohen, the former acting undersecretary for intelligence and analysis at DHS, told ABC News this incident is an example of the real-world warning DHS issued last week.
"DHS and law enforcement officials have repeatedly warned that violent extremists will target for violence public officials and others whom they perceive as holding views that conflict with their extremist ideological beliefs," Cohen, also an ABC News contributor, said. "While in this case, law enforcement officials appear to have prevented violence, we are in the midst of a highly volatile threat environment and we can expect more acts of violence by lone offenders and extremist groups in the weeks ahead."
Those charged on Saturday will make their first court appearance on Monday.
ABC News' Michelle Mendez contributed to this report.