(NewsNation) — Police in Richmond, Virginia, said Wednesday that they thwarted a planned July 4 mass shooting after receiving a tip that led to the arrest of two men and the seizure of multiple guns — an announcement that came just two days after a deadly mass shooting on the holiday in a Chicago suburb.

A “hero citizen” overheard a conversation indicating there was an attack on the city’s popular Independence Day celebration being planned and called police to report it, Police Chief Gerald Smith said at a news conference.

“I’m thankful for the hero citizen who called in because they heard something, they heard these two individuals who are potentially plotting to cause mass casualties and mass chaos in the city of Richmond during our Fourth of July fireworks show,” Richmond Mayor Levar Stoney told NewsNation “Rush Hour” in an exclusive interview.

Police initiated an investigation, along with the U.S. Department of Homeland Security and FBI, which led to the arrests of two men, Rolman Balacarcel and Julio Alvarado-Dubon, on charges of being a non-U.S. citizen in possession of a firearm. More charges are possible.

During an appearance on NewsNation’s “Dan Abrams Live,” Smith declined to say if the two men entered the country legally, but did say they were not on the police’s radar.

Smith credited the tipster and his officers for playing vital roles in preventing a tragedy.

“It’s just a combination of good police work and being alert in the kind of conditions we’re living under when it comes to mass shootings,” Smith said on NewsNation’s “Dan Abrams Live” on Wednesday.

Officers seized two assault rifles, a handgun and hundreds of rounds of ammunition from a residence where the firearms and “related material” were in plain view, Smith said. Stoney called them “weapons of war.”

Police arrested one of the suspects while searching the residence and found the other after using “surveillance” to track him down, Stoney said.

The two men were being held without bond at a local jail, the chief said.

No information is yet available on the motivation of the two men, Stoney said.

The apparent thwarted plot was planned for the same day that a gunman opened fire from a rooftop during a Fourth of July parade in the affluent Chicago suburb of Highland Park, killing seven people and injuring more than three dozen.

Stoney called on members of Congress to further work on finding a solution to preventing mass shootings.

“This is not the way that Americans, young and old, should have to live in any of their communities, no matter where they live in this country,” Stoney said.

Robert E. Crimo III was charged with seven counts of murder Tuesday. The shooting sent hundreds of people fleeing in fear and set off an hourslong manhunt. Authorities have not yet identified a motive in that shooting.

The Associated Press contributed to this report.