When they were digging up Sally they said something like... "Wow we gave the guy at the gate 20 bucks, and he said "go wild" like nothing unusual was happening, like this happens every night."
The night security guard has a profitable sideline in looking the other way.
Necrophiliacs? Graverobbers? Or wannabe Doctor Frankensteins? ...Oh and Vampires of course who were buried by accident by their human families.