A few weeks ago he was doing the same thing in another area of the park, as shown HERE.
Problem is, he uses a spade shovel instead of a trowel to dig for his "treasure" . . .
and leaves mounds (tripping hazards) when placing the sod back into the freshly dug holes.
Apparently, he hasn't been caught on the park's video surveillance system yet.
(There is a video surveillance system, isn't there?)