Soldiers participating in a training exercise on a Mississippi military base heard it Tuesday and Wednesday — noises they believed were gunshots around the fringes of Camp Shelby.

On edge after a gunman attacked military members in Chattanooga, Tennessee, authorities began looking for a maroon pickup truck that the soldiers described from the Tuesday incident. They found it late Wednesday morning when Alfred Baria Sr. drove past officers on a state highway just south of New Augusta.

The Mississippi Bureau of Investigation took him into custody at gunpoint, with officials calling a bomb squad into sparsely populated Perry County east of Hattiesburg to investigate plastic pipes and other items they found in the truck.

But the 61-year-old Baria told authorities that it wasn't gunshots at all, just the backfiring of his battered Isuzu. That's a story backed up by his son in an interview Wednesday evening with The Associated Press. Alfred Baria Jr. said his dad's pickup backfires loudly every time someone shifts gears and steps on the gas.

And those pipes? Two big, long ones were for plumbing a newly built auto repair shop in the backyard, Alfred Baria Jr. said. Small pipe containers with caps were for storing auto parts and hardware, he said, showing a reporter one on a shelf inside the shop.

His father though, is in trouble, charged not only with four misdemeanor counts of disturbing the peace but also two felony counts of being a felon in possession of a gun. Alfred Baria Jr. said the rifle and pistol were his, and he didn't realize that his father, previously convicted on drug charges, couldn't be anywhere on the property with them.

Perry County Sheriff Jimmy Dale Smith and MBI spokesman Warren Strain said officials were still questioning the elder Baria, who's being held in the Perry County jail. Smith said Baria would likely be appointed a lawyer at a bail hearing scheduled Thursday. Though Strain emphasized that more charges could still be filed, for now Baria isn't charged with any crime that indicates he shot at the National Guardsmen and active duty Army soldiers training at Camp Shelby.

The Barias' mobile home is in a remote area of Perry County bordered by miles of pine trees in the DeSoto National Forest and Camp Shelby. The son said his father was driving along the southern border of Camp Shelby to buy parts or hardware in nearby Brooklyn, Mississippi, when soldiers heard the noises.

At Camp Shelby, guards at all base entrances were armed under a recent order from Mississippi Gov. Phil Bryant, Lt. Col. Christian Patterson said. After the second incident, Bryant said in a statement that the shootings underscored why he signed that executive order July 20.

"The soldiers at Camp Shelby and across the state can and should take appropriate steps to defend themselves as necessary," Bryant said.

The large military base south of Hattiesburg is one of the premier training facilities for National Guard troops from across the country and during the height of the Iraq war was often the last stop for National Guard troops training to go to the Middle East.

The base is hosting about 4,600 active-duty soldiers, National Guard and reservists from Texas and Mississippi in a summer training exercise.

This summer's training focuses on teaching troops how to operate on the platoon level — generally about 30 soldiers to a group, although that can vary.