That was, indeed, "one hell of an amen" Brantley Gilbert -- to quote a song of his.

Because when the shots rang out on that fateful day back in July and U.S. Marine Gunnery Sgt. Thomas Sullivan, U.S Marine Staff Sgt. David Wyatt, U.S. Marine Sgt. Carson Holmquist, U.S. Marine Lance Cpl. Skip Wells and U.S. Navy Petty Officer Randall Smit were killed in the otherwise beautiful city of Chattanooga, Tennessee.  Gilbert knew that he had to do something.

And on Sept. 16, exactly two months after the tragic events, he did.

CHATTANOOGA UNITE: A TRIBUTE ON THE RIVER was a daylong celebration that included a parade, fireworks and a free concert by Gilbert, including his hit anthem “One Hell of an Amen.”

"It's shocking, ya know, I can leave my living room and be at that recruitment office in less than two hours," Gilbert told an interviewer at WTVC. "That hits home. It started off real small as an acoustic, really intimate event, and as the thought process and the time went along, we just thought the families and the community deserved a more grand gesture."

Chattanooga native Samuel L. Jackson was also on hand to lend some inspirational words to the crowd gathered at the Riverband Barge stage.

Tricia Despres is the contributing editor for Rare Country, based out of Chicago, Illinois. Join the conversation on Twitter at @RareCountry. We would love to see y’all there.