A man driving an armor-plated military-type vehicle and firing what appeared to be a machine gun mounted on top caused a ripple of panic in suburban Detroit on the Fourth of July.

It turned out the weapon was a modified World War II .50-caliber machine gun that had been converted to fire compressed gas. It produced bright flashes and loud gunfire sounds as the driver, a man in his 40s, drove around Shelby Township.

Recordings of a series of 911 calls capture the fear of residents whose reports of the imposing sight sent officers swarming late Thursday. In one call, bangs similar to the sound of gunshots can be heard.

Police say they arrested the driver, identified as John Lind, and confiscated his vehicle. He was released the next day but was not charged.

Lind is a veteran and the founder and director of Detroit Arsenal for Democracy, a museum specializing in World War II military vehicles.