It hit Charmaine like the sweet kiss of a wrecking ball. Derek had been the one who had stolen the office's entire supply of staples. Derek had been the one who'd installed cameras in the womens restrooms. Derek had forwarded everyone's phones to the Pentagon. Derek had embezzled the department slush fund. And it was Derek who stood before her now with a finger on the button of the detonator of the cardigan bomb she was wearing, the sweater that had been his Christmas gift to her at the office party.
He was -- the Deadly Practical Joker.
Source: Unexplained Cinema