Do we know the exact reason why the U3 halt was in

Do we know the exact reason why the U3 halt was initiated? Was it the large volume of extra shares hitting the market that day or was it initiated by COR regarding the dividend issue? Not that it matters necessarily, but I would imagine it's one way the short party(ies) could ensure they'd make maximum dollars by causing the stock to be halted and the share price to plummet (along with the extra shares).

Thanks Chas!