SPOILER WARNING: The following article contains major spoilers for Heroes in Crisis #4 by Tom King, Clay Mann, Tomeu Morey and Clayton Cowles, on sale now.
The concept of Sanctuary is a new one to the DC Universe, and its existence has therefore been mostly unknown to the world at large. Even after the superhero massacre that occurred at the mental health facility, the news was confined to the superhuman community. That is, until Tom King and Clay Mann's Heroes in Crisis #4, where a notable DC character breaks the news to the world. The way readers learn of the reveal, though, evokes another well-known classic superhero tale.
Since its onset, the series has interspersed nine-panel sequences representing confidential videos from various characters admitted to Sanctuary. The videos featuring the admissions, confessions and other secret discussions, however, have been leaked to the press by an unknown figure known as The Puddler. The Puddler has an apparent problem with Sanctuary's residents, and the videos he's disclosed have gone to none other than Lois Lane. As a dutiful reporter, and recognizing she's sitting on one of the biggest stories of the decade, she subsequently reveals the existence of Sanctuary, and the recent massacre.
The nine-panel layouts are a common aspect of King's storytelling methods, deliberately homaging the method used by artist Dave Gibbons throughout his and Alan Moore's legendary Watchmen. Heroes in Crisis' latest issue, though, evokes Moore and Gibbons' story in a more direct fashion.
Of course, Superman has known about the massacre from the beginning; he was one of the first responders on the scene, so Sanctuary has probably been a matter of discussion in Lois and Clark's household many times over. Clark has therefore also known about Lois' pending story, but as a reporter himself realizes it wouldn't be his place to make her story known prior to publication – even to Superman's colleagues.
As you would expect, when Batman discovers this, he's none too happy with Superman withholding Sanctuary's pending reveal.
The only reason Superman breaks his silence now is because Lois' story has just now gone live. His exact words to Batman and Wonder Woman are, "She sent it 35 seconds ago." If that quote sounds familiar, it's because the line paraphrases that of Adrian Veidt, aka Ozymandias, in the penultimate chapter of Watchmen.
"I did it 35 minutes ago," were Veidt's disconcerting words to Nite Owl and Rorschach as he unveiled his master plan to unify the world. That plan consisted of a much larger massacre involving the death of millions in Veidt's genocidal attempt to bring mankind together against a common enemy: himself. Geoff Johns and Gary Frank's Doomsday Clock, of course, has shown that Veidt's plan didn't unify the world for long, and in fact only delayed its destruction.
Do the similarities imply that Heroes in Crisis is setting the stage for a potential far-reaching disaster along the lines of Watchmen? Well, not necessarily. On the surface, King and Mann's sequence appears to be only an homage to Moore and Gibbons' own. It's worth noting, though, that early in the series, Watchmen didn't give much indication to the pending enormity of its later scope, either, and both did start off as a superhero murder mystery, after all.