Having worked with online marketing in the past, there are companies/individuals that offer services to run your social media to free up your time. They should run the messaging through the marketing managers/owners in the actual company first, though if they aren't careful you get crossed messaging due to not switching accounts.

I wonder which company/org/person was hired to do this & which social management software (if any) they are using. Often you should have the next week's tweets written a week or two in advance so they can be automatically pushed on time, freeing up the writer for an occasional vacation &/or illness.