Based soley on the very sketchy details in the article I think it's as likely the guy was playing a really dumb prank on a coworker (or else a real bomb scare to his work) and just tried to pass it off as a mistaken gaming comment. Unless his friend is really dumb and couldn't tell he was talking to someone else.
And I don't remember any GTA missions that involved bombing something where you give a rats ass about getting anyone else out of the building.