A “hero citizen” overheard a conversation suggesting an attack on an Independence Day celebration in the capital was being planned and called police to report it, Police Chief Gerald Smith told a news conference. The caller said the attack was planned for the Dogwood Dell Amphitheater, where an annual fireworks show is held, Smith said. “One phone call saved many lives on the Fourth of July,” Smith said. Police launched an investigation along with the U.S. Department of Homeland Security and the FBI, which led to the arrest of two men on charges that they were not U.S. citizens and in possession of a firearm, Smith said. He said additional charges are possible. Julio Alvarado-Dubon, 52, was arrested July 1, the same day police received the tip, Smith said. He said police have placed a second suspect, Rolman Alberto Balacarcel, 38, under surveillance since that day, but did not initially have probable cause to arrest him. He was arrested Tuesday in Albemarle County, near Charlottesville, and was being held in a local jail. Police spokeswoman Tracy Walker said both men are from Guatemala. Initial documents filed in Richmond General District Court state that both Alvarado-Dubon and Balacarcel are not in the US legally. The documents said Alvarado-Dubon has an expired visa. The documents did not include details about the alleged plot. Smith said the two men lived together in a home in Richmond, where officers seized two handguns, a handgun and hundreds of rounds of ammunition in plain view. He said police have not determined a motive for the planned attack. Richmond Mayor Levar Stoney, who attended the news conference along with city council members, decried what he called an epidemic of gun violence across the country. “Whether you’re at home on the cul-de-sac, or in your neighborhood, or in a park, or at a parade, out to eat — you have to keep your head on a spinning wheel,” Stoney said. “And that’s not the country I know I want to live in … but these are the facts right now.” Court documents say bail was set at $15,000 for Alvarado-Dubon on Wednesday, but it was unclear if he had been released. The documents say he has lived in the Richmond area for three years and works full-time in the construction industry. A preliminary hearing is scheduled in Richmond on Aug. 2. Online records showed Balacarcel was in custody at a local jail. It was not immediately clear if he had an attorney who could speak on his behalf. The apparently foiled plot was hatched on the same day 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. Robert E. Crimo III was charged with seven murders on Tuesday. The shooting sent hundreds of people fleeing in fear and set off an hours-long manhunt. Authorities have yet to determine a motive for the shooting.