The phantom weed wacker

A few weeks ago, motion caught my eye as I was walking through my living room. I looked out, convinced I'd seem something .... well, something not right in my neighbor's yard.
Their grass was fairly tall at this point. It was well-maintained, just a little tall as though they too hadn't had time to cut it.
Just as I decided there was no movement outside, a figure stepped from behind their evergreen tree. Clad in camouflage, the figure wielded a weed wacker sort of instrument. Using it, he cut a swath, about a foot wide and four feet across, into the tall grass. He didn't seem to be aiming at anything but the grass, and he cut the strip in a visible spot next to the driveway. Then he disappeared behind the tree.
"Honey, you've got to see this," I called to my husband. "I think the neighbor turned into a lawn ninja."
But it didn't look like my neighbor, from the two-inch diameter circle of skin shown by the camo hoodie pulled tight around the face.
"What's he doing?" my husband asked, equally fascinated.
Then, the phantom moved on to the next lawn. There, he swiped at a few dandelions, sending their heads flying.
He skipped the next house and delved into the lawn next to it, presumably finding some other sort of vegetation that needed wacking. From there, we lost sight of him.
If he ever really existed.
We haven't seen him sense. And pretty soon, the evidence of his visit was obscured by lawn mowers.
He hit multiple lawns, so he can't be a neighbor. He was on food in camos, so he can't be from a lawn service. He only hit random spots, be it grass or weed, so his goal couldn't have been killing weeds.
We're baffled.