From WHEC:

On a holiday that celebrates our nation’s freedom, the very people who’ve fought for our rights to enjoy, sometimes have a hard time participating. Chad Curtis is the program manager at Warrior Salute Veteran Services in Webster, a non-profit that assists veterans with PTSD.

"Whether they're in a rear position or they're on the forward lines of combat, there's mortars, exploding grenades, obviously gun fire. The sound of fireworks is very similar to the sound of a mortar attack where you're just standing there and something is blowing up next to you, it's the surprise element and the sound is very similar with a lot of larger fireworks," he says.