UFO sighting?

At 6:35 this evening I was walking my dog along the shore in Atlantic Beach, between Oceanana Pier and Sportsman's Pier (sadly closed for good last week, and dark) when I heard a low rumbling sound, sort of like thunder. It wasn't that loud and sort of blended with the sound of the surf, so I didn't take immediate notice, but after a few seconds I looked toward the water.

I saw a line of four orange-ish lights, sort of like roman candles, moving mainly horizontally and a little up. They were clearly miles out over the water, and I estimated 6-8 degrees above the horizon. They lasted several seconds then faded out. Then another line of lights issued apparently from some unseen aircraft (it was already pitch black) moving in a slightly different direction. Those lasted a few seconds too. Once they faded I saw nothing more, and the sound soon died out.

I have no idea what it was, except maybe a training exercise involving military jets and live fire with tracer rounds or something. Or else we're being invaded by aliens.

It was a little spooky. Sort of a "what the hell is that?....JESUS, WHAT THE HELL IS THAT????" reaction.