I don't know much about drones but what I saw appeared to be a fixed wing but flew like a quadcopter. That part had me confused.

Did some quick googling and discovered that there are hybrid drones and a couple that popped up look like the silhouette I saw in the night sky. One in particular is a mapping drone.

It was pretty clear to me by the pattern they were flying in they were searching or something based on the fact they were staggered but flying in the same direction. Not sure if mapping is done most effectively at night, but they they must have been recording some sort of information.

Something like this or this