While police said they prevented one shooting, Mayor Levar Stoney said at a press conference that there was a attack at Cyber Cafe in downtown Richmond that injured six people during the early hours of July 4. The shooter remains at large.

A 911 caller told authorities of overhearng a plot targeting the Dogwood Dell, a 2,400-seat amphitheater that hosted a Fourth of July celebration and fireworks show, Richmond Chief Gerald Smith said during a press conference.

Police did not provide details on why they thought a mass shooting was planned.

The tip led Richmond Police officers, along with Homeland Security and FBI agents to a home in the city on July 1. They seized two assault rifles, a handgun and 223 rounds of ammunition there and arrested a suspect, identified as Julio Alvarado, on gun charges.

A second suspect, Rolman Balcarcel, was arrested on July 5 after investigators said they collected enough probable cause in relation to the mass shooting threat.

Both men are non-U.S. citizens who lived in the home where the ammunition and guns were seized. They are being held at the Richmond City Jail. No further information about the suspects was available.

(Reporting by Randi Love in New York; Editing by David Gregorio)

By Randi Love