Yes been covered before, it's a fake.
Oberon
We did similar at the end of our course, previous courses had been done for their farewell party trick as they were still present, so we decided to do ours that wouldn't be apparent till long after we were long gone. We used a large amount of fuel drained from a jet and killed the grass outside the DI's office with the same words and his name.......... A following course in the block let us know it was mission complete as it showed from the stairwell of the block after a week or so... Much to the DI's chargrin. Seeding it never worked, so they had to returf and that showed up for months.
