False fireflies

I was sitting on my wooden houses’ concrete ledge with three of my friends, staring at the pool of green grass before us. It stretched out for miles without a tree in sight. A grey tinge dulled everything except a small dot of green light hovering inches above the grass.
I took it to be a firefly and just enjoyed its glow.
As my friends and I started to get up to leave, the firefly’s light expanded. Soon it grew to be the size of a basketball.
It hovered in place while four more basketball-sized circles of green light surrounded it as we stared in awe. Once they arranged themselves on either side of the first light, they flew to the right, toward a horizontal green slit that had appeared a few feet from the ground.

After they disappeared, the air smelled of dried blood.