Exchange was flooded and that Con Edison was shutting off all power to New York City during the storm.
Both "breaking" news posts were refuted by authorities, but not before being retweeted hundreds of times, sparking panic as the massive storm devastated the US East Coast and claimed dozens of lives.
After going silent for several hours, on Tuesday evening @ComfortablySmug offered "the people of New York a sincere, humble and unconditional apology."
"During a natural disaster that threatened the entire city, I made a series of irresponsible and inaccurate tweets," the user wrote.
"While some would use the anonymity and instant feedback of social media as an excuse, I take full responsibility for my actions."
The Buzzfeed online news site had earlier identified @ComfortablySmug as a 29-year-old hedge fund analyst and the campaign manager of New York Republican congressional candidate Christopher Wright.
@ComfortablySmug did not identify himself or herself in the mea culpa, but confirmed that he or she had resigned from Wright's campaign.
Wright's campaign website said Tuesday that his campaign manager had resigned and been replaced, without providing further details.
Angry Twitter users had heaped criticism on @ComfortablySmug after the postings were shown to be made-up, and many remained furious after the apology, saying the prank had given social media a bad name.
"Kudos on your direct apology and owning up to your bad behavior. But why?" wrote Joe Grossberg at @grossberg.
"You're only sorry you got caught. Have a nice life hating yourself scumbag!" wrote Tom Reynolds at @tomreynolds.
Others called on @ComfortablySmug to make amends to storm victims and to reporters who might have been put in danger by trying to verify the claims.
"You sir, are an example of Twitter at its worst. How about you help rescue victims on, say Long Island?" Viviane at @viviane212 wrote, referring to one of the hardest-hit areas.